Gabby had some chocolate bars. She sold 30% of her chocolate bars and gave half of the remainder to her sister. After that, she bought 42 chocolate bars and had a total of 63 chocolate bars in the end. How many chocolate bars did Gabby have at first?
Percentage of chocolate bars that Gabby left after selling 305 of her chocolate bars
= 100% - 30%
= 70%

Fraction of chocolate bars that Gabby had left after giving to her sister
= ¹₂ x 70%
= ⁷₂₀

Number of chocolate bars that Gabby had left = 7 u

Number of chocolate bars that Gabby had in the end = 7 u + 42

7 u + 42 = 63
7 u = 63 - 42
7 u = 21

1 u = 21 ÷ 7 = 3

Total number of chocolate bars that Gabby had at first
= 20 u
= 20 x 3
= 60

Answer(s): 60