There are 150 marbles in a box. 0.4 of them are purple marbles, and the rest are grey and black marbles. If there are 14 as many grey marbles as black marbles. How many black marbles are there?
| Purple marbles |
Grey marbles |
Black marbles |
Total |
| 2 u |
3 u |
5 u |
| |
1 p |
4 p |
|
0.4 =
410 =
25 Fraction of marbles that are grey and black marbles
= 1 -
25 =
35 Total number of marbles = 5 u
5 u = 150
1 u = 150 ÷ 5 = 30
Number of grey marbles and black marbles
= 3 u
= 3 x 30
= 90
Number of grey and black marbles
= 1 p + 4 p
= 5 p
5 p = 90
1 p = 90 ÷ 5 = 18
Number of black marbles
= 4 p
= 4 x 18
= 72
Answer(s): 72
