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

1. What was the percentage decrease in the number of highlighters sold from Jul to Aug?
2. There were 72 more highlighters sold in Sep than in Jul. How many highlighters were sold in Sep?
3. The average number of highlighters sold from Jul to Nov was 138. What was the average number of highlighters sold in Oct and Nov?

(a)
Percentage decrease in the number of highlighters from Jul to Aug
= ^{5 - 3}₅ x 100%
= ²₅ x 100%
= 40%

(b)
Difference in the number of intervals between Sep and Jul
= 9 - 5
= 4

4 intervals → 72

1 interval → 72 ÷ 4 = 18

Number of highlighters sold in Sep
= 9 intervals
= 9 x 18
= 162

(c)
Total intervals from Jul to Sep
= 5 + 3 + 9
= 17

Total number of highlighters sold from Jul to Sep
= 17 intervals
= 17 x 18
= 306

Total number of highlighters sold from Jul to Nov
= 5 x 138
= 690

Number of highlighters sold from Oct to Nov
= 690 - 306
= 384

Average number of highlighters sold in Oct and Nov
= 384 ÷ 2
= 192

Answer(s): (a) 40%; (b) 162; (c) 192