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Whole Numbers (Pri-6)

/ Whole Numbers Greenwood Primary School / Homework (2018)
Some pupils sat for a sci test.Tthe averge marks for the sci test was 76.4 marks.However one of the pupils score was wrongly recorded as 94 instead of 76 as a result the average marks was wrongly calculated as 78.4.How many pupils sat for the sci test ? 
Ra

August 21, 2018
 
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Difference in averages = 78.4 - 76.4 = 2 marksDifference in score for 1 pupil = 94 - 76 = 18So total number of pupils =18 ÷ 2 = 9  (ans)
0

August 21, 2018
Ra
idk ho to do this sorr
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Comments 1
Aug 25, 2018 04:04 AM
Hi Rachel, try following the working found in the answer which is verified (has a GREEN TICK on the answer)
August 25, 2018
Let U be the total marks for all other pupils & N be total students, thenCase 1: no errorU + 76N = 76.4  -> U = 76.4N - 76---Case 2: with errorU + 94N = 78.4  -> U = 78.4N - 94---So 76.4N - 76 = 78.4N - 94                  2N = 18                    N = 9  (ans)
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Comments 1
Aug 22, 2018 02:15 AM
This method is algebra so not recommended but it shows thinking behind.
August 22, 2018
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