Question

Please answer this question. ( use SOLVE BY ASSUMING method.)

A science quiz consists of 15 questions. 2 marks are awarded for every correct answer and 1 mark is deducted for every wrong answer. Kelly scores 21 marks for the science quiz. How many questions does she answer correctly?

Answer 1

${\huge {\mathfrak {Answer :-}}}$

Let the number of correct questions attended be 'x' and number of incorrect attended be 'y'.

➡️ So, x + y = 15.

Or, y = 15 - x

Now, we have,

➡️ 2x - y = 21.

Or, 2x - 15 + x = 21

Or, 3x = 21 + 15 = 36

Or, x = 36/3 = 12.

And, putting the value of x,

➡️ y = 15 - x = 15 - 12 = 3.

$<b>Hence, Kelly attends 12 correct answers and 3 incorrect answer. </b>$

➡️ Recheck,

12(2) + 3(-1)

= 24 - 3 = 21. ⬅️

$<b>$ That's it..