Question

In a mathematics competition each correct answer gains 5 marks. However, 1 mark is
deducted for each incorrect answer. Mary answered 30 questions for a total of 78 marks.
Determine the number of correct and incorrect questions Mary answered.

Answer 1

Answer:

answer -18 right answer and 12 wrong answer

Answer 2

Answer:

The number of correct and incorrect questions Mary answered are 18 and 12 respectively.

Step-by-step explanation:

let the correctly answered questions be x and incorrectly answered questions be y.

then marks awarded for correctly answered questions are 5x and marks deducted for incorrectly answered questions are -y.

total question she answered = x + y = 30____(1)

total marks she obtained = 5x - y = 78_____(2)

add (1) and (2), which gives 6x = 108____(3)

from (3) x = 108/6 = 18 substitute this in (1)

then, y = 30 - 18 = 12