Solution: let the water injection speed of small water pipes be x cubic meters and that of large water pipes be 4X cubic meters. According to the meaning of the question:

( 1/2V)/X+( 1/2V)/4X = t

(2V)/4X+( 1/2V)/4X=t

2.5V/(4X)=t

X=5V/(8t)

∴4X=5V/(2t)

Therefore, the water injection speed of small water pipes is 5V/(8t) m3, and that of large water pipes is 5V/(2t) m3.

Note: The speed ratio of small water pipes and large water pipes is actually their cross-sectional area ratio. That is, the area ratio of the circle: 1: 4.