SOLUTION: Hello and thank you for answering my question! Monica bats in 9 cricket matches. In the tenth match, he makes 9 runs and his average decreases by two. How many runs has he made

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Question 972108: Hello and thank you for answering my question!
Monica bats in 9 cricket matches. In the tenth match, he makes 9 runs and his average decreases by two. How many runs has he made in all?
If convenient, please include an explanation! Thank you once again!

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Monica bats in 9 cricket matches.
In the tenth match, he makes 9 runs and his average decreases by two.
How many runs has he made in all?
:
let a = average of the first 9 matches
then
(a-2) = average of all 10 matches
:
the equation to find a
%289a+%2B+9%29%2F10 = (a - 2)
multiply both sides by 10
9a + 9 = 10(a-2)
9a + 9 = 10a - 20
9 + 20 = 10a - 9a
29 = a, average of the first 9 games
:
"How many runs has he made in all? "
total runs in all 10 matches
r = 9(29) + 9
r = 261 + 9
r = 270 runs in all
:
:
Check this by finding the average of all 10 matches, should be 2 less than 29
%289%2829%29+%2B+9%29%2F10 = 270%2F10 = 27