Jaslyn had 378 erasers. ²₇ were white and the rest were blue and silver. The ratio of the number of blue erasers to the number of silver erasers was 1 : 5. Jaslyn decided to buy some more white erasers to increase the number of white erasers to half of the total number of erasers.

1. How many less blue erasers than white erasers did he have at first?
2. How many more white erasers did he have to buy?

White erasers	Blue erasers	Silver erasers	Total
2x6	5x6
	1x5	5x5
12 u	5 u	25 u	378

	White erasers	Blue erasers	Silver erasers
Before	12 u	5 u	25 u
Change	+ ?
After	30 u	30 u
Comparing white, blue and silver erasers in the end	1	1

(a)
The total number of blue erasers and silver erasers is repeated. Make the total number of blue erasers and silver erasers the same.  LCM of 5 and 6 is 30.

Total number of erasers at first
= 12 u + 5 u + 25 u
= 42 u

42 u = 378

1 u = 378 ÷ 42 = 9

Number of less blue erasers than white erasers at first
= 12 u - 5 u
= 7 u
= 7 x 9
= 63

(b)
Number of more white erasers that Jaslyn had to buy
= 30 u - 12 u
= 18 u
= 18 x 9
= 162

Answer(s): (a) 63; (b) 162