PSLE
The bar graph shows the number of notebooks sold from Jan to Mar. The number of notebooks sold is not shown on the scale.

1. What was the percentage increase in the number of notebooks sold from Jan to Feb?
2. There were 128 less notebooks sold in Jan than in Mar. How many notebooks were sold in Jan?
3. The average number of notebooks sold from Jan to May was 164. What was the average number of notebooks sold in Apr and May?

(a)
Percentage increase in the number of notebooks from Jan to Feb
= ^{5 - 2}₂ x 100%
= ³₂ x 100%
= 150%

(b)
Difference in intervals between Mar and Jan
= 10 - 2
= 8

8 intervals → 128

1 interval → 128 ÷ 8 = 16

Number of notebooks sold in Jan
= 2 intervals
= 2 x 16
= 32

(c)
Total intervals from Jan to Mar
= 2 + 5 + 10
= 17

Total number of notebooks sold from Jan to Mar
= 17 intervals
= 17 x 16
= 272

Total number of notebooks sold from Jan to May
= 5 x 164
= 820

Number of notebooks sold from Apr to May
= 820 - 272
= 548

Average number of notebooks sold in Apr and May
= 548 ÷ 2
= 274

Answer(s): (a) 150%; (b) 32; (c) 274