PSLE A box contained gold and black beads. At first, the number of gold beads was
15 the number of black beads. After
23 of the gold beads and
19 of the black beads were used, 387 beads were left.
- What fraction of the beads were left? Leave your answer in the simplest form.
- How many beads were used?
|
Gold |
Black |
Comparing gold beads and black beads at first |
1x9 = 9 u |
5x9 = 45 u
|
Before
|
3x3 = 9 u |
9x5 = 45 u |
Change
|
- 2x3 = - 6 u |
- 1x5 = - 5 u |
After
|
1x3 = 3 u |
8x5 = 40 u |
(a)
The number of black beads at first is repeated. Make the number of black beads at first the same.
LCM of 5 and 9 is 45.
The number of gold beads at first is repeated.
Since the number of gold beads at first is 9 u, we make the total number of gold beads at first the same by multiplying 3 by 3 to become 9 u too.
Fraction of the beads left
=
3 + 409 + 45 =
4354 (b)
Number of beads left
= 3 u + 40 u
= 43 u
43 u = 387
1 u = 387 ÷ 43 = 9
Number of beads used
= 6 u + 5 u
= 11 u
= 11 x 9
= 99
Answer(s): (a)
4354; (b) 99