In January, Betty and Justin had erasers in the ratio 9 : 7. In February, each of them gave away the same number of erasers. Betty then had five times as many erasers as Justin.

1. Find the ratio of the number of erasers Justin had in January to the number of erasers he had in February.
2. Find the ratio of the total number of erasers both had in January to the total number of erasers both had in February.

	Betty	Justin	Difference
Before	9x2 = 18 u	7x2 = 14 u	2x2 = 4 u
Change	- 13 u	- 13 u
After	5x1 = 5 u	1x1 = 1 u	4x1 = 4 u

(a)
Since Betty and Justin gave away the same number of erasers, the difference in the number of erasers between Betty and Justin at first and in the end remains the same.

Make the difference in the number of erasers at first and in the end the same. LCM of 2 and 4 is 4.

Justin's erasers in January : Justin's erasers in February
14 : 1

(b)
Total number of erasers in January
= 18 u + 14 u
= 32 u

Total number of erasers in February
= 5 u + 1 u
= 6 u

Total erasers in January : Total erasers in February
32 : 6 _(÷2)
16 : 3 

Answer(s): (a) 14 : 1; (b) 16 : 3