Justin had to solve some Social Studies questions during a 3-week school holidays. At the end of the first week, the ratio of the number of questions solved to the number of questions unsolved was 3 : 7. At the end of the second week, Justin solved another 27 questions and the number of unsolved questions became ¹₄ of the total number of questions. How many questions did Justin need to solve on the third week to complete his assignment?

	Solved	Unsolved	Total
First week	3x2 = 6 u	7x2 = 14 u	10x2 = 20 u
Second week	+ 27	- 27
Third week	3x5 = 15 u	1x5 = 5 u	4x5 = 20 u

Total number of questions remains same.
LCM of 4 and 10 = 20

Number of questions that Justin solved at the end of the second week
= 15 u - 6 u
= 9 u

9 u = 27

1 u = 27 ÷ 9 = 3

Number of questions that Justin needed to complete on the third week
= 5 u
= 5 x 3
= 15

Answer(s): 15