SOLUTION: Naomi had an average score of 70 on her science tests. On her next test, she got a 90 and her average jumped 5 points to 75. How many science tests has Naomi taken?

Question 880618: Naomi had an average score of 70 on her science tests. On her next test, she got a 90 and her average jumped 5 points to 75. How many science tests has Naomi taken?
Found 2 solutions by ankor@dixie-net.com, polas4sure@gmail.com:
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Naomi had an average score of 70 on her science tests.
On her next test, she got a 90 and her average jumped 5 points to 75.
How many science tests has Naomi taken?
:
Let n = no. of tests taken
then
(n-1) = total number taken before she got a 90
:
= 75
multiply both sides by n
70n - 70 + 90 = 75n
20 = 75n - 70n
20 = 5n
n = 20/5
n = 4 tests taken
:
:
You can check this yourself in the original equation
Answer by polas4sure@gmail.com(2) (Show Source): You can put this solution on YOUR website!
Naomi had an average score of 70 on her science tests. On her next test, she got a 90 and her average jumped 5 points to 75. How many science tests has Naomi taken?
SOLUTION:
let the No. be x
(x - 1), then
{70.(x - 1) 90}/x = 75
therefore
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