PSLE Ethan kept his black and red buttons in two boxes. The ratio of the number of black to red buttons in the first box was 1 : 2 and it was 3 : 4 in the second box. The two boxes contained the same number of buttons. What fraction of Ethan's buttons were black buttons?
First box |
Second box |
1x21 21 u |
1x21 21 u |
3x7 |
7x3 |
Black |
Red |
Black |
Red |
1x7 |
2x7 |
3x3 |
4x3 |
7 u |
14 u |
9 u |
12 u |
The total number of buttons in the first box and the second box is the same. Make the total number of buttons in each box the same. LCM of 3 and 7 is 21.
Total number of black buttons
= 7 u + 9 u
= 16 u
Total number of buttons
= 21 u + 21 u
= 42 u
Fraction of Ethan's buttons that were black buttons
=
1642 =
821 Answer(s):
821