The mean of ten positive numbers is 16. When another number is added, the mean becomes 18. Find the eleventh number.
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:
- Option A is incorrect.
- Option B is not correct.
- C is correct.
- D is not the correct answer.
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 /