Tom has some white and gold marbles. The total mass of all his marbles is 233 g. He has 7 less white marbles than gold marbles. The average mass of the white marbles is 8 g. The average mass of the gold marbles is 9 g. How many marbles does Tom have altogether?
| |
White |
Gold |
Total |
| Number |
1 u |
1 u + 7 |
2 u + 7 |
| Value |
8 |
9 |
|
| Total value |
8 u |
9 u + 63 |
233 |
Total mass of white marbles
= 1 u x 8
= 8 u
Total mass of gold marbles
= 9(1 u + 7)
= 9 u + 63
Total mass of the marbles
= 8 u + 9 u + 63
= 17 u + 63
17 u + 63 = 233
17 u = 233 - 63
17 u = 170
1 u = 170 ÷ 17 = 10
Total number of marbles
= 2 u + 7
= 2 x 10 + 7
= 20 + 7
= 63
Answer(s): 63
