Andy has some green and grey marbles. The total mass of all his marbles is 191 g. He has 5 more grey marbles than green marbles. The average mass of the green marbles is 6 g. The average mass of the grey marbles is 7 g. How many marbles does Andy have altogether?
| |
Green |
Grey |
Total |
| Number |
1 u |
1 u + 5 |
2 u + 5 |
| Value |
6 |
7 |
|
| Total value |
6 u |
7 u + 35 |
191 |
Total mass of green marbles
= 1 u x 6
= 6 u
Total mass of grey marbles
= 7(1 u + 5)
= 7 u + 35
Total mass of the marbles
= 6 u + 7 u + 35
= 13 u + 35
13 u + 35 = 191
13 u = 191 - 35
13 u = 156
1 u = 156 ÷ 13 = 12
Total number of marbles
= 2 u + 5
= 2 x 12 + 5
= 24 + 5
= 35
Answer(s): 35
