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

1. What was the percentage decrease in the number of pens sold from Aug to Sep?
2. There were 77 more pens sold in Sep than in Jul. How many pens were sold in Aug?
3. The average number of pens sold from Jul to Nov was 129. What was the average number of pens sold in Oct and Nov?

(a)
Percentage decrease in the number of pens 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 pens sold in Aug
= 10 intervals
= 10 x 11
= 110

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

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

Total number of pens sold from Jul to Nov
= 5 x 129
= 645

Number of pens sold from Oct to Nov
= 645 - 209
= 436

Average number of pens sold in Oct and Nov
= 436 ÷ 2
= 218

Answer(s): (a) 20%; (b) 110; (c) 218