Diana spent $42 on some staplers, files and pens. The number of staplers she bought was ¹₂ the number of files. The number of pens she bought was ⁴₅ the number of files. The ratio of the amount of money she spent on the staplers, files and pens was 7 : 6 : 1. The files were sold at 5 for $9. Find the price of 1 stapler.

Amount spent
Staplers	Files	Pens	Total
7 u	6 u	1 u	$42

Total amount that Diana spent on staplers, files and pens
= 7 u + 6 u + 1 u
= 14 u

14 u = 42

1 u = 42 ÷ 14 = 3

Amount that Diana spent on files
= 6 u
= 6 x 3
= $18

Number of sets of files of 5 bought
= 18 ÷ 9
= 2

Number of files that Diana bought
= 2 x 5
= 10

Number of items bought
Staplers	Files	Pens	Total
1x5	2x5
	5x2	4x2
5 p	10 p	8 p	23 p

The number of files bought is repeated.  Make the number of files bought is the same.  LCM of 2 and 5 is 10.

Number of files that Diana bought = 10 p

10 p = 10

1 p = 10 ÷ 10 = 1

Number of staplers that Diana bought
= 5 p
= 5 x 1
= 5

Amount that Diana spent on staplers
= 7 u
= 7 x 3
= $21

Price of 1 stapler
= 21 ÷ 5
= $4.20

Answer(s): $4.20