guerrero25
There are 17 students in a certain class. On the day the test was given, Taqeesha was absent. The other 16 students took the test, and their average was 77. The next day, Taqeesha took the test, and with her grade included, the new average is 78. What is Taqeesha’s grade on the test?
A. 78
B. 80
C. 87
D. 91
E. 94
I took this question from
Magoosh . I saw somebody coming up with a very quick solution -
"When Taqeesha took the test, the average increased from 77 to 78. That means, Taqeesha scored 78 plus 1 mark for each one of the other students. i.e., 78 + 16 = 94." approach is unclear
I could easily solve this using the conventional way i.e with average formula . I would like to understand the above approach . Also, Kindly help me with some similar questions that I can practice to make sure I nail this concept well .
As always , thank you !
Using the conventional method of average would be easier if the numbers are small but can be time consuming if the values are too high.
Let us say that 16 students scored 77 marks on Day 1. So average is obviously 77.
Next day when Taqeesha appears for the test, the average rises to 78.
So let's assume that all of them score 78.
So, we need to increase 1 mark in all previous 16 students and add 78 marks of Taqeesha.
So, 78 + 1 * 16 = 94.
Hence option E.
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