Elijah has some red and purple marbles. The total mass of all his marbles is 196 g. He has 7 more purple marbles than red marbles. The average mass of the red marbles is 3 g. The average mass of the purple marbles is 4 g. How many marbles does Elijah have altogether?
| |
Red |
Purple |
Total |
| Number |
1 u |
1 u + 7 |
2 u + 7 |
| Value |
3 |
4 |
|
| Total value |
3 u |
4 u + 28 |
196 |
Total mass of red marbles
= 1 u x 3
= 3 u
Total mass of purple marbles
= 4(1 u + 7)
= 4 u + 28
Total mass of the marbles
= 3 u + 4 u + 28
= 7 u + 28
7 u + 28 = 196
7 u = 196 - 28
7 u = 168
1 u = 168 ÷ 7 = 24
Total number of marbles
= 2 u + 7
= 2 x 24 + 7
= 48 + 7
= 28
Answer(s): 28
