In a coin box, the ratio of the number of pink balls to the number of white balls was 1 : 4. Each time, 5 pink and 6 white balls were taken out of the coin box. A while later, only 70 white balls were left in the coin box. What was the total number of balls in the coin box at first?

	Pink balls	White balls
Before	1x5 = 5 u	4x5 = 20 u
Change	- 5 u	- 6 u
After	0	70

Since there is no pink balls left, this means that the number of pink marbles at first is the same as the number of pink marbles taken out.  

Make the number of pink balls at first and taken out the same.  LCM of 1 and 5 is 5.

Number of white balls in the end
= 20 u - 6 u
= 14 u

14 u = 70

1 u = 70 ÷ 14 = 5

Total number of balls in the coin box at first
= 5 u + 20 u
= 25 u
= 25 x 5
= 125

Answer: 125