Two trains 14

Two trains running in the same direction at 40kmph and 22kmph completely pass one another in 1 minute. If the length of the first train is 125m, find the length of the 2nd train.

Correct answer:

b =  175 m

Step-by-step explanation:

$$\begin{gathered} v_1=40\text{km/h}\to \text{m/s}=40:3.6\text{m/s}=11.11111\text{m/s} \\ {v}_2=22\text{km/h}\to \text{m/s}=22:3.6\text{m/s}=6.11111\text{m/s} \\ t=1\text{min}\to \text{s}=1\cdot 60\text{s}=60\text{s} \\ a=125\text{m} \\ v=v_1-v_2=11.1111-6.1111=5\text{m/s} \\ v=\frac{s}{t}=\frac{a+b}{t} \\ v\cdot t=a+b \\ b=v\cdot t-a=5\cdot 60-125=175\text{m} \end{gathered}$$

Try another example