Solve problems using scale drawings
Construct accurate labelled scale drawings, measure unknowns and convert back to real lengths while keeping scale, precision and north assumptions explicit.
Exam scope and assessment notes
Shared Foundation/Higher Construction covers F4.5A–D: measurement and drawing, triangles and other 2D shapes, scale drawings, and both straight-edge-and-compasses bisectors. These six original lessons are linked to those syllabus rows; the links do not establish complete textbook coverage or specialist approval. Use the named instruments and retain your marks, arcs and joins. A numerical answer or displayed reference alone does not show instrument skill. Physical millimetre work needs a real ruler and a verified object or calibrated print; recheck calibration after printing, resizing or zooming. Measure only diagrams explicitly supplied as accurate for measurement. Virtual drawing units do not certify physical millimetres. Written answers and model comparisons are for self-checking, with no marks, mastery or formal assessment approval. The source is linear 4MA1 Issue 2, checked against November 2026/June 2027 entry context; regional options depend on centre eligibility. Modular qualifications remain separate. Publisher chapter links are navigation aids: the relevant final chapter body and Teaching Hub content remain unverified. Other syllabus sections remain separate.
Before you begin
- Convert metres and centimetres and use a positive ratio scale.
- Construct segments and included angles with ruler, protractor and compass transfers.
- Use declared north, clockwise three-figure bearings and perpendicular directions.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
At scale 1:250, what drawing length represents a real length of 20 m?
What you will learn
- Convert real lengths to drawing lengths using compatible units and a stated positive scale.
- Construct a route, room plan or triangle before measuring its unknowns.
- Interpret approximate drawing readings without replacing construction by exact trigonometry or inferring unrelated map credit.
Place your own instruments and retain the joins, rays and arcs. The givens are shown first; your construction stays at the positions you choose.
Worked construction
At a scale of 1 cm represents 20 m, draw a route 80 m east and then 60 m north. Construct the perpendicular directions with ruler and protractor as appropriate, label the scale and measure the straight start-to-finish distance on your drawing. Convert that reading to metres, keeping the result approximate.
Drawing unit: cm. Printed graduations calibrate the virtual drawing; they do not certify physical paper or monitor size.
All submitted joins and arcs stay visible. Select a recorded ruler or protractor to inspect its graduations; other instruments retain their actual footprints. Long lines and rays are cropped to this viewing frame.
Coordinates describe the virtual drawing in cm; they are placement controls, not endpoint readings. Positive angles turn anticlockwise; negative sweeps turn clockwise. Clicking chooses a visible position. It does not move an instrument onto a reference answer.
Read or use my recorded ruler
These readings come from your actual ruler placement. A misplaced ruler keeps its offset; this tool does not report the ideal endpoint reading.
Find intersections of my retained traces
Intersections use the actual arc sweeps and line extents. A full circle or supporting line cannot supply a crossing outside a traced arc, ray or segment.
This is a fixed mathematical comparison. A complete written response records an attempt; a teacher still needs to review the reasoning. Virtual graduations do not establish physical ruler, protractor or compass skill, and no marks or mastery are awarded. Verify physical calibration and recheck it after any print or zoom change.
State the scale and convert compatible units
A scale explains how drawing lengths relate to real lengths. A statement such as one centimetre represents a given number of metres can be used directly in those units. For a ratio 1:n, first put both lengths into the same unit: divide the real length by n to obtain its drawing length, or multiply the drawing length by n to recover the real one.
Use a positive scale and choose drawing lengths that fit the available paper. Write the scale beside the diagram so a measurement can be interpreted later. A labelled virtual drawing uses its stated unit system, but a physical centimetre construction requires physical calibration; arbitrary zoom or a resized print changes the physical lengths unless the scale is restored.
Draw the given data, then measure the unknown
Use a ruler for the converted lengths and a protractor for the specified directions or angles. Retain the rays and label the known values. For a route, draw each leg from the correct preceding endpoint. For a triangle, place the included angle at its named vertex. Only after the accurate construction is complete should you join or measure the requested unknown distance.
When a drawing uses north bearings, draw the declared parallel north lines and measure clockwise at each named origin. When a plan specifies the placement of an object, preserve those supplied offsets as givens rather than inventing a convenient position. A not-to-scale sketch can organise the problem but cannot be used as an accurate measurement source.
Carry the reading precision back through the scale
Measure the unknown on the finished drawing with the requested precision, then multiply by the real amount represented by one drawing unit. State the result as approximate: rounding to the nearest millimetre on a drawing does not become exact real-world knowledge. A coarser scale can make a small drawing error represent a larger real distance.
The private mathematical model may have an exact root or an ideal intersection. Those values check that the task is coherent; they do not replace actual construction and measurement. A room-plan fit is a geometric comparison under its stated dimensions, not a safety or access certification. Scale-drawing work here does not automatically establish the whole map/similarity or bearing programme, even where publisher navigation co-tags those topics.
Sources for this lesson
Pause and explain
A drawing reading is about 2.6 cm and the scale is 1 cm represents 15 m. What real distance does it indicate?
Worked example
At a scale of 1 cm represents 20 m, draw a route 80 m east and then 60 m north. Construct the perpendicular directions with ruler and protractor as appropriate, label the scale and measure the straight start-to-finish distance on your drawing. Convert that reading to metres, keeping the result approximate.
Show the worked solution
- Convert the given route legs using the scale: 80÷20=4 cm east, then 60÷20=3 cm north from the end of the first leg.
- Draw and label the two perpendicular legs. Join the route’s starting point to its final point with a straight segment; do not measure only one route leg or add the legs as the straight separation.
- Measure that straight segment on the accurate drawing. Its ideal reference is 5 cm, so a nearby drawing reading should be interpreted as approximately 5 cm.
- Convert back using the labelled scale: about 5×20=100 m. This is the straight separation inferred from a measured scale drawing, not an exact Pythagoras-only solution or the 140 m travelled route length.
Answer Draw 4 cm east and 3 cm north at the stated scale. The straight separation has reference reading about 5 cm, giving approximately 100 m.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Using scale 1:50, construct a 6 m by 4.5 m rectangular room outline and a 1.2 m-wide doorway along the bottom wall starting at the lower-left corner. Draw a 1.5 m by 0.75 m rectangular table, parallel to the room edges, with its lower-left corner placed 4 cm right and 3 cm up from the lower-left corner on the drawing. These placement offsets are supplied drawing givens. Use a ruler for the scaled lengths and a protractor for the right-angle directions, retaining the construction rays. Label the scale and dimensions and check the table fits inside the outline.
Give me a hint
Convert every real dimension to centimetres before dividing by 50. Do not scale the supplied drawing-position offsets a second time.
Compare my reasoning
- The room dimensions are 600 cm and 450 cm in real units. Divide by 50 to draw a rectangle 12 cm by 9 cm, retaining its perpendicular corner construction.
- The doorway is 120÷50=2.4 cm wide on the drawing, starting at the supplied lower-left corner along the bottom wall.
- The table dimensions are 150÷50=3 cm and 75÷50=1.5 cm. Use the stated 4 cm-right, 3 cm-up drawing placement, then draw its sides parallel to the room edges.
- The table extends to 7 cm right and 4.5 cm up within the 12 cm by 9 cm outline, so it lies inside. These given-position and size checks do not certify actual door access or safety.
At 1:50 draw the room 12 cm×9 cm, doorway 2.4 cm and table 3 cm×1.5 cm at the supplied drawing offsets. The table outline lies inside the room.
Look for these in your work
- Use compatible centimetre units for every 1:50 size conversion.
- Actually construct the room, doorway and table with the stated placement.
- Label the scale and check geometric fit without claiming a real safety or access assessment.
Draw triangle ABC at a scale of 1 cm represents 10 m, with AB=90 m, AC=70 m and included angle BAC=60°. Construct the lengths and the named angle yourself. Measure BC on the completed accurate drawing to the nearest millimetre, convert that reading to metres and label the real-distance answer approximate.
Give me a hint
The scale makes the two given drawing sides 9 cm and 7 cm; measure the third side only after construction.
Compare my reasoning
- Convert and draw AB=90÷10=9 cm. At A use a protractor to construct the upper 60° ray from AB, and mark AC=70÷10=7 cm on that ray.
- Join B to C and retain the given-angle ray and length marks. BC is an unknown of the completed drawing, not a prelabelled side.
- Measure BC to the nearest millimetre. The ideal drawing length is about 8.185 cm, whose nearest-millimetre reference is 82 mm=8.2 cm.
- Convert the reported reading: about 8.2×10=82 m. The exact private model is approximately 81.85 m, but that model value is not an exact learner-drawing claim or a replacement for the measured 82 m result.
Construct 9 cm and 7 cm drawing sides with the 60° included angle. Reference BC reading: about 82 mm=8.2 cm, indicating approximately 82 m.
Look for these in your work
- Construct the two scaled lengths and the included angle at A.
- Measure the previously unknown BC to the nearest drawing millimetre.
- Convert the rounded reading to about 82 m and keep the precision distinction explicit.
Posts A and B are 120 m apart east-west, with B east of A. Marker C has bearing 030° from A and 330° from B, with parallel north lines. At 1 cm represents 20 m, construct AB and the two north-bearing rays, locate C by their intersection and measure AC and C’s perpendicular height above AB to the nearest millimetre of drawing. Convert both readings to real metres.
Give me a hint
Use clockwise bearings at their own origins. After the two rays meet north of AB, measure lengths on the drawing rather than using trigonometry.
Compare my reasoning
- Draw AB=120÷20=6 cm east-west and the declared parallel north lines at A and B. Use a protractor to construct the clockwise 030° and 330° rays at their named origins.
- The two northward rays meet at C. Retain the bearing marks, join AC and use a perpendicular direction to measure the height above AB; neither length is an initial answer label.
- AC has ideal drawing length 6 cm, giving a nearest-millimetre reference of 60 mm. This reading represents about 6×20=120 m.
- The height’s ideal drawing length is about 5.196 cm, which rounds to 52 mm=5.2 cm. Convert the rounded reading to about 5.2×20=104 m; the private model height is about 103.92 m. These are measured scale-drawing comparisons, not exact trigonometric task methods.
Construct the two bearing rays and their intersection. Reference readings: AC≈60 mm=6 cm→about 120 m; perpendicular height≈52 mm=5.2 cm→about 104 m.
Look for these in your work
- Construct the 6 cm base and clockwise bearings from parallel north at the correct origins.
- Locate C by actual ray intersection and measure both requested drawing lengths.
- Convert nearest-millimetre readings to approximate real distances and avoid an exact-model shortcut.
Common mistakes
- Using a ratio scale on mixed metres and centimetres without conversion.
- Measuring an unknown from an uncalibrated or not-to-scale sketch, or replacing the construction with a formula-only answer.
- Reporting a rounded scale-drawing result as exact or treating a plan-fit/bearing co-tag as complete map, similarity or safety approval.
What can you explain now?
A student measures an unknown from a sketch explicitly labelled “not to scale”. Can multiplying that reading by a guessed scale make the result valid?
Compare with the explanation
No. The problem needs an explicitly accurate scale drawing and its stated calibration.
A guessed multiplier cannot restore unknown distortions in a sketch. Construct the given lengths and directions at a labelled scale before measuring and converting the unknown.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Recall how a ratio scale needs common units, how a measured drawing length becomes a real length, and why the reading remains approximate. Explain which instrument evidence must precede the unknown measurement.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.