In an examination one mark is awarded for every correct answer and 4 mark is deducted for every wrong answer. A student answered 120 questions and got 90 marks. How many questions he answered correctly?

Asked by bis0584 | 30th May, 2015, 10:44: PM

Expert Answer:

L e t space t h e space n u m b e r space o f space c o r r e c t space q u e s t i o n s space b e space apostrophe x apostrophe space a n d space n o. space o f space i n c o r r e c t space q u e s t i o n s space b e space apostrophe y apostrophe. x plus y equals 120 rightwards double arrow 4 x plus 4 y equals 480.... left parenthesis i right parenthesis x minus 4 y equals 90...... left parenthesis i i right parenthesis left parenthesis i right parenthesis plus left parenthesis i i right parenthesis comma 5 x equals 570 x equals 114  x plus y equals 120 y equals 120 minus 114 y equals 6  N o. space o f space c o r r e c t space q u e s t i o n s space equals space 114

Answered by Prasenjit Paul | 31st May, 2015, 07:26: PM

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