Gabby had some coin collection.
13 of them were black and the rest were red. She gave away 156 of the red coins and 30% of the black coins. She then had
14 of her coin collection left. How many coins did Gabby give away?
| |
Black |
Red |
Total |
Total |
Before
|
1x4 =
4 u |
2x4 =
8 u |
3x4 =
12 u |
4x3 =
12 u |
Change
|
- 0.3x4 =
- 1.2 u |
- 156 |
|
- 3x3 =
- 9 u |
After
|
0.7x4 =
2.8 u |
8 u - 156 |
|
1x3 =
3 u |
The total number of coins that Gabby had at first is repeated. Make the total number of coins at first the same. LCM 3 and 4 is 12.
Number of black coins that Gabby gave away
= 30% x 1 u
=
30100 x 1 u
= 0.3 u
1.2 u - 156 = 9 u
9 u - 1.2 u = 156
7.8 u = 156
1 u = 156 ÷ 7.8 = 20
Number of coins that Gabby gave away
= 9 u
= 9 x 20
= 180
Answer(s): 180
