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 P6 Maths Problem - Average
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By: parent603 (offline)  Monday, February 20 2012 @ 08:07 PM CST (Read 1024 times)  
parent603

Five different whole numbers are arranged in order from the smallest to the greatest. The average of the first three numbers is 10. The average of the middle three numbers is 14. The average of the last three numbers is 25. Given the number in the centre is 17, find the other four numbers.

Could someone advise on how to solve this Q? Really appreciate your help! Thanks! Smile

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By: hci (offline)  Tuesday, February 21 2012 @ 09:45 AM CST  
hci

Hi Let these 5 numbers be a,b,c,d,e

(1) Ave of a,b and c is 10, that means total sum of the three numbers is 10x3=30

c being the middle number is 17, hence a+b = 30-17=13

so sum of a and b is 13, ave of a and b will be 13/2=6.5

hence a would be 6 and b would be 7

so we have a=6, b=7, c=17

(2) Ave of b, c and d is 14, total sum of the three numbers is 14x3=42

b+c = 7+17=24, hence d= 42-24=18

(3) Ave of c,d and e is 25. total sum of the three numbers is 25x3=75

since c=17 and d=18, e=75-17-18=40

thus, the other four numbers are 6,7,18 and 40.

Hope it helps!

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By: parent603 (offline)  Tuesday, February 21 2012 @ 07:22 PM CST  
parent603

Quote by: hci

Hi Let these 5 numbers be a,b,c,d,e

(1) Ave of a,b and c is 10, that means total sum of the three numbers is 10x3=30

c being the middle number is 17, hence a+b = 30-17=13

so sum of a and b is 13, ave of a and b will be 13/2=6.5

hence a would be 6 and b would be 7

so we have a=6, b=7, c=17

(2) Ave of b, c and d is 14, total sum of the three numbers is 14x3=42

b+c = 7+17=24, hence d= 42-24=18

(3) Ave of c,d and e is 25. total sum of the three numbers is 25x3=75

since c=17 and d=18, e=75-17-18=40

thus, the other four numbers are 6,7,18 and 40.

Hope it helps!



I have been thinking about this problem for 2 weeks. Thanks alot. Laughing Out Loud

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