The mean of seven numbers is 21. Five of the numbers are 18,23,21,17,and 19. One of the remaining numbers is 3/4 of the other remaining number. What are the two unknown numbers?
Mathematics · Middle School · Tue Nov 03 2020
llm
Answered on
Given :
Mean = 21
Five numbers are : 18,23,21,17,and 19
Let the 6th number be x
Then, 7th number is 3x/4 or 0.75x
We know ,
Mean = sum of terms/number of terms
21 = (18 + 23 + 21 + 17 + 19 + x + 0.75x)/7
21 = (98 + 1.75x)/7
147 = 98 + 1.75x
1.75x = 147 - 98
1.75x = 49
x = 49/1.75
x = 28
Then, 7th number = 28 × 3/ 4
= 21
Hence, two unknown numbers are 28 and 21.