Tammy had 90% as many chocolate bars as Opal. Tammy gave away 20% of her chocolate bars and Opal bought another 20 chocolate bars. As a result, Tammy now has 70% as many chocolate bars as Opal. Find the number of chocolate bars that Opal had at first.
| |
Tammy |
Opal |
| Before |
9x7 |
10x7 |
| Change |
- 1.8x7 |
+ 20 |
| After |
7.2x7 |
10x7 + 20 |
Comparing Tammy and
Opal in the end |
7x7.2 |
10x7.2 |
| |
Tammy |
Opal |
| Before |
63 u |
70 u |
| Change |
- 12.6 u |
+ 20 |
After
|
50.4 u
|
70 u + 20 =
72 u |
90% =
90100 =
91020% x 9
=
20100 x 9
= 1.8
70% =
70100 =
710The number of chocolate bars that Tammy had in the end is repeated.
Make the number of chocolate bars that Tammy had in the end the same.
The number of chocolate bars that Opal had in the end is repeated.
70 u + 20 = 72 u
72 u - 70 u = 20
2 u = 20
1 u = 20 ÷ 2 = 10
Number of chocolate bars that Opal had at first
= 70 u
= 70 x 10
= 700
Answer: 700
