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The mean of ten positive numbers is 16…

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MATHS

The mean of ten positive numbers is 16. When another number is added, the mean becomes 18. Find the eleventh number.

A. 3

B. 16

C. 38

D. 30

QUICK ANSWER…

C

DETAILS…

If the mean of ten positive numbers is 16, and when another number is added to bring the mean to 18, the eleventh number will be =

Mean = sum of all numbers/ how many numbers being added

Let sum of all the numbers = A

Mean = A/10

A = 10 × mean

A = 10 × 16

A = 160

If another number is added, let the number be = B

New mean = (A + B)/11

18 = (160 + B)/11

18 × 11 = 160 + B

198 = 160 + B

B = 198 – 160

B = 38

Now for the right answer to the above question:

  1. Option A is incorrect.
  2. Option B is not correct.
  3. C is correct.
  4. D is not the correct answer.

KEY-POINTS…

You may please note these/this:

  • Mean = sum of numbers / number of occurrence of numbers

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/ culled from 2021 JAMB-UTME MATHEMATICS question 23 /

1 Answers

  1. 0 Votes Thumb up 0 Votes Thumb down 0 Votes

    Mean = sum of all the numbers involved / how many numbers that is involved.

    Admin - Mar 29, 2022 | Reply


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