Rachel had some pen collection.
12 of them were grey and the rest were black. She gave away 171 of the black pens and 50% of the grey pens. She then had
23 of her pen collection left. How many pens did Rachel give away?
| |
Grey |
Black |
Total |
Total |
Before
|
1x3 =
3 u |
1x3 =
3 u |
2x3 =
6 u |
3x2 =
6 u |
Change
|
- 0.5x3 =
- 1.5 u |
- 171 |
|
- 1x2 =
- 2 u |
After
|
0.5x3 =
1.5 u |
3 u - 171 |
|
2x2 =
4 u |
The total number of pens that Rachel had at first is repeated. Make the total number of pens at first the same. LCM 2 and 3 is 6.
Number of grey pens that Rachel gave away
= 50% x 1 u
=
50100 x 1 u
= 0.5 u
1.5 u - 171 = 2 u
2 u - 1.5 u = 171
0.5 u = 171
1 u = 171 ÷ 0.5 = 342
Number of pens that Rachel gave away
= 2 u
= 2 x 342
= 684
Answer(s): 684
