In a stationery kiosk, the number of folders was ¹₃ of the total number of folders and correction tapes together. Tim sold the folders and correction tapes in sets of 1 folder and 10 correction tapes. After selling all the correction tapes, he still had 20 folders left. How many correction tapes were in the stationery kiosk at first?

	Folders	Correction Tapes
Before	1x5 = 5 u	2x5 = 10 u
Change	- 1x1 =  - 1 u	- 10x1 = - 10 u
After	20	0

Since all the correction tapes were sold, the number of correction tapes at first and the number of correction tapes sold were the same.  Make the number of correction tapes at first and sold the same.  LCM of 2 and 10 is 10.

Number of folders sold
= 5 u - 1 u
= 4 u

4 u = 20

1 u = 20 ÷ 4 = 5

Number of correction tapes at first
= 10 u
= 10 x 5
= 50

Answer(s): 50