Question

Yan has already finished Three-fifths of the 45 math problems he was assigned today. Each math problem took him 1 four-fifths of a minute to complete. If this pace continues, how much more time, to the nearest minute, will the rest of the problems take him to finish?

Answer 1

`\boxed{\sf 18\ problems = 22\ minutes}`

Explanation:

Yan has finished =
`(3)/(5) of \ 45 \ maths \ problems`

Yan has finished =
`(3)/(5) * 45`

=> 3 * 9

=> 27 problems

Yan has problem left:

=> 45 - 27

=> 18 problems

1 problem =
`1 (4)/(5)` of a minute

1 problem = 1.2 minutes

18 problems = 1.2 * 18

18 problems = 21.6 minutes

18 problems ≈ 22 minutes

Answer 2

`\boxed{\sf 32 \ minutes}`

Explanation:

Yan finished 3/5 of 45 math problems.

`(3)/(5) * 45=27`

Yan finished 27 math problems.

`\sf 1(4)/(5) \ of \ a \ minute= 108 \ seconds=1.8 \ minutes`

Yan has
`45-27=18` problems left.

1 problem = 1.8 minutes

18 problems =
`1.8* 18=32.4` minutes

32.4 minutes to nearest minute will be 32 minutes.