There are 20% as many green marbles as grey marbles in Ivory's collection of marbles. The number of red marbles is 30% fewer than the number of grey marbles. There are 320 more red marbles than green marbles.

1. Find the total number of marbles in the collection.
2. What percentage are the number of grey marbles as compared to the number of red marbles? Leave your answer as a mixed number in its simplest form.

Green	Grey	Red
1x2	5x2
	10x1	7x1
2 u	10 u	7 u

(a)
20% = ²⁰₁₀₀ = ¹₅

100% - 30% = 70%
70% = ⁷⁰₁₀₀ = ⁷₁₀

The number of grey marbles is the repeated identity. Make the number of grey marbles the same.  LCM of 5 and 10 is 10.

Number of more red marbles than green marbles
= 7 u - 2 u
= 5 u

5 u = 320

1 u = 320 ÷ 5 = 64

Total number of marbles in the collection
= 2 u + 10 u + 7 u 
= 19 u
= 19 x 64
= 1216

(b)
Percentage of the number of grey marbles as compared to the number of red marbles
= ¹⁰₇ x 100%
= ¹⁰⁰⁰₇ %
= 142⁶₇ %

Answer(s): (a) 1216; (b) 142⁶₇ %