A car drove from city a to city B at a speed of 40 kilometers per hour. After three hours of driving, due to rain, the speed was reduced by 10 kilometers, 45 minutes later than the expected time. It is necessary to find the distance between city a and city B

A car drove from city a to city B at a speed of 40 kilometers per hour. After three hours of driving, due to rain, the speed was reduced by 10 kilometers, 45 minutes later than the expected time. It is necessary to find the distance between city a and city B

Let the distance between the two places be a, then the estimated time is a / 40, and the actual use time is a / 40 + 45 / 60. The equation is obtained. A = 40 * 3 + (40-10) (A / 40 + 45 / 60-3). Through the equation, a = 120-3a / 4 + 22.5-90 is obtained. Finally, a = 210 is calculated