Nick has some brown and blue marbles. The total mass of all his marbles is 200 g. He has 10 less brown marbles than blue marbles. The average mass of the brown marbles is 3 g. The average mass of the blue marbles is 7 g. How many marbles does Nick have altogether?
| |
Brown |
Blue |
Total |
| Number |
1 u |
1 u + 10 |
2 u + 10 |
| Value |
3 |
7 |
|
| Total value |
3 u |
7 u + 70 |
200 |
Total mass of brown marbles
= 1 u x 3
= 3 u
Total mass of blue marbles
= 7(1 u + 10)
= 7 u + 70
Total mass of the marbles
= 3 u + 7 u + 70
= 10 u + 70
10 u + 70 = 200
10 u = 200 - 70
10 u = 130
1 u = 130 ÷ 10 = 13
Total number of marbles
= 2 u + 10
= 2 x 13 + 10
= 26 + 10
= 70
Answer(s): 70
