In a test, two people will have to answer 100 questions each. They score 3 points for each correct answer. The test has not ended yet. Each person has already answered 90 questions. Person R has answered 70% of the first 90 questions correctly. Person S has answered 50% of the first 90 questions correctly. What is the minimum number of points that Person R must get from the last 10 questions to win the test?

	Person R	Person S
Current total score	189	135
Additional score if the remaining questions are answered correctly	+ -21	+ 30
Final total score	168	165
	Winner

Score that Person R has earned so far
= 70% x 90 x 3
= ⁷⁰₁₀₀ x 90 x 3
= 189

Score that Person S has earned so far
= 50% x 90 x 3
= ⁵⁰₁₀₀ x 90 x 3
= 135

Remaining questions that each person has to answer
= 100 - 90
= 10

If Person S answers the last 10 questions correctly, the additional score that he will earn
= 10 x 3
= 30

Total score that Person S will earn after answering all the questions
= 135 + 30
= 165

Number of points that Person S is leading Person R by
= 165 - 189
= -24

For Person R to win the test, the number of points he has to earn
= -24 + 3
= -21

Answer(s): -21