Vaidev has some grey and silver marbles. The total mass of all his marbles is 205 g. He has 7 less grey marbles than silver marbles. The average mass of the grey marbles is 10 g. The average mass of the silver marbles is 15 g. How many marbles does Vaidev have altogether?
| |
Grey |
Silver |
Total |
| Number |
1 u |
1 u + 7 |
2 u + 7 |
| Value |
10 |
15 |
|
| Total value |
10 u |
15 u + 105 |
205 |
Total mass of grey marbles
= 1 u x 10
= 10 u
Total mass of silver marbles
= 15(1 u + 7)
= 15 u + 105
Total mass of the marbles
= 10 u + 15 u + 105
= 25 u + 105
25 u + 105 = 205
25 u = 205 - 105
25 u = 100
1 u = 100 ÷ 25 = 4
Total number of marbles
= 2 u + 7
= 2 x 4 + 7
= 8 + 7
= 105
Answer(s): 105
