Jack has some yellow and green marbles. The total mass of all his marbles is 215 g. He has 5 less yellow marbles than green marbles. The average mass of the yellow marbles is 8 g. The average mass of the green marbles is 9 g. How many marbles does Jack have altogether?
| |
Yellow |
Green |
Total |
| Number |
1 u |
1 u + 5 |
2 u + 5 |
| Value |
8 |
9 |
|
| Total value |
8 u |
9 u + 45 |
215 |
Total mass of yellow marbles
= 1 u x 8
= 8 u
Total mass of green marbles
= 9(1 u + 5)
= 9 u + 45
Total mass of the marbles
= 8 u + 9 u + 45
= 17 u + 45
17 u + 45 = 215
17 u = 215 - 45
17 u = 170
1 u = 170 ÷ 17 = 10
Total number of marbles
= 2 u + 5
= 2 x 10 + 5
= 20 + 5
= 45
Answer(s): 45
