From the total stroke length, the ratio of each stroke length is 1:2:3.

Uphill length: 60* 1/( 1+2+3)

Transverse slope length: 60*2/( 1+2+3)

Downhill length: 60*3/( 1+2+3)

When going uphill, the speed is 3 kilometers per hour, and the ratio of three periods is 4: 5: 6.

Uphill time: [60* 1/( 1+2+3)]/3

Grading time: [60 *1/(1+2+3)]/3 * (5/4)

Downhill time: [60 *1/(1+2+3)]/3 * (6/4)

Therefore, it always takes time.

[60 *1(1+2+3)]/3 * (1+5/4+6/4) = 74/9 (hours)