Tim has some black and white marbles. The total mass of all his marbles is 250 g. He has 10 more white marbles than black marbles. The average mass of the black marbles is 10 g. The average mass of the white marbles is 15 g. How many marbles does Tim have altogether?
| |
Black |
White |
Total |
| Number |
1 u |
1 u + 10 |
2 u + 10 |
| Value |
10 |
15 |
|
| Total value |
10 u |
15 u + 150 |
250 |
Total mass of black marbles
= 1 u x 10
= 10 u
Total mass of white marbles
= 15(1 u + 10)
= 15 u + 150
Total mass of the marbles
= 10 u + 15 u + 150
= 25 u + 150
25 u + 150 = 250
25 u = 250 - 150
25 u = 100
1 u = 100 ÷ 25 = 4
Total number of marbles
= 2 u + 10
= 2 x 4 + 10
= 8 + 10
= 150
Answer(s): 150
