A machine stitches 6 shirts every hour. Draw the graph of shirts against hours, and find (i) the shirts stitched in 4½ hours (ii) the time taken to stitch 21 shirts.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Write what is given and what is to be found. 6 shirts per hour. To find: shirts in 4½ hours, and the time for 21 shirts.
2 · Write the relation. y = 6x, where x is hours and y is shirts. Direct variation with k = 6.
3 · Make the table of values. x = 1, 2, 3, 4, 5, 6 gives y = 6, 12, 18, 24, 30, 36.
4 · Write the scale. x-axis 2 cm = 1 hour; y-axis 1 cm = 3 shirts.
5 · Plot and draw. Plot the six points and join them with a ruler. The line passes through O.
6 · Read the answers.
(i) x = 4.5 gives y = 27 shirts
(ii) y = 21 gives x = 3.5 hours
7 · Check and box the answer. 6 × 4.5 = 27 and 21 ÷ 6 = 3.5. Box: 27 shirts; 3½ hours.
Scoring tip: Write the relation and k before the table. Show both readings with dotted lines on the graph.
