Question

Gavin had 20 minutes to do a three problem quiz he spent 9 3/4 minutes on problem 1 and 3 4/5 minutes on problem 2 how much time did he have left for problem 3 write the answer in minutes and seconds how many minutes did he have left

Answer 1

Gavin had 20 minutes to do a three-problem quiz.

He spent 9 3/4 minutes on problem 1.

He spent 3 4/5 minutes on problem 2.

How much time did he have left for problem 3?

We need to add the time spent on problem 1 and problem 2 and then subtract the sum from the total time.

`20-(9(3)/(4)+3(4)/(5))`

Simplify the above fraction

`\begin{gathered} 20-(9(3)/(4)+3(4)/(5)) \\ 20-\lbrack(9+3)((3)/(4)+(4)/(5))\rbrack \\ 20-\lbrack(12)((5\cdot3+4\cdot4)/(20))\rbrack \\ 20-\lbrack(12)((15+16)/(20))\rbrack \\ 20-\lbrack(12)((31)/(20))\rbrack \\ 20-12(31)/(20) \\ 20-\frac{12\cdot20+31_{}}{20} \\ 20-\frac{271_{}}{20} \\ (20\cdot20-1\cdot271)/(20) \\ (400-271)/(20) \\ (129)/(20) \end{gathered}`

Let us write the answer in mixed number

`(129)/(20)=6(9)/(20)`

Finally, convert the fractional part to seconds by multiplying the fractional part by 3

`6(9)/(20)=6(27)/(60)`

This means that there are 6 minutes and 27 seconds are left for problem 3.

`6(27)/(60)`