SOLUTION: A student missed 3 problems on a mathematics test and recieved a grade of 81%. if all the problems were of equal value, how many problems were on the test? Round off your answer to

Question 414520: A student missed 3 problems on a mathematics test and recieved a grade of 81%. if all the problems were of equal value, how many problems were on the test? Round off your answer to the nearest interger
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Note: 81% in decimal form is 0.81 (drop the % and move the decimal 2 spots to the left)

Say there are x problems total.

So if you missed 3 problems, then that means you got problems correct. Eg: x=20, so you got x-3=20-3=17 problems correct

Now all we need to do is divide the number of problems you got correct by the total number of problems to get the decimal form of the percentage.

So we get

Now multiply both sides by x to get

Now let's solve for x

So (roughly). Round to the nearest whole number to get 16

So there are 16 problems total.

Note: this means that you got 16-3 = 13 problems correct. So 13/16 = 0.8125 which is close enough to 0.81 giving us the percentage 81%

If you need more help, email me at jim_thompson5910@hotmail.com

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Jim
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