PSLE
The bar graph shows the number of markers sold from Jul to Sep. The number of markers sold is not shown on the scale.

1. What was the percentage decrease in the number of markers sold from Aug to Sep?
2. There were 77 more markers sold in Sep than in Jul. How many markers were sold in Aug?
3. The average number of markers sold from Jul to Nov was 145. What was the average number of markers sold in Oct and Nov?

(a)
Percentage decrease in the number of markers from Aug to Sep
= ^{10 - 8}₁₀ x 100%
= ²₁₀ x 100%
= 20%

(b)
Difference in the number of intervals between Sep and Jul
= 8 - 1
= 7

7 intervals → 77

1 interval → 77 ÷ 7 = 11

Number of markers sold in Aug
= 10 intervals
= 10 x 11
= 110

(c)
Total intervals from Jul to Sep
= 1 + 10 + 8
= 19

Total number of markers sold from Jul to Sep
= 19 intervals
= 19 x 11
= 209

Total number of markers sold from Jul to Nov
= 5 x 145
= 725

Number of markers sold from Oct to Nov
= 725 - 209
= 516

Average number of markers sold in Oct and Nov
= 516 ÷ 2
= 258

Answer(s): (a) 20%; (b) 110; (c) 258