of his usual speed. He was a 20-minute delay. Formula used: Distance = Speed × Time Calculation:Let the distance be D and his speed be S So, his usual time to reach the office =
D
S
Now, his new speed =(
4
5
)S According to the question, {
D
(
4
5
)
S}−(
D
S
)=20 minutes (5
D
4
S)−(
D
S
)=(
20
60
) hours (
D
4
S)=
1
3
hours (
D
S
)=
4
3
hours {(
4
3
)times60} minutes =80 minutes ∴ His original time to reach the office is 80 minutes.