Question 890789
Distance(d) equals Rate(r)times Time(t)or d=rt;r=d/t and t=d/r
Let r=train B's speed
Then r+20=train A's speed
Time required for train A to travel 210 mi=210/(r+20)
Time required for train B to travel 170 mi=170/r
Now we are told that these times are equal, so:
210/(r+20)=170/r  divide each term by 10 to simplify
21/(r+20)=17/r  multiply each term by r(r+20)
21r=17(r+20)  expand
21r=17r+340 subtract 17r from each side
4r=340
r=85 mph---Train B's speed
r+20=85+20=105 mph---train A's speed

CK
210/105 =170/85
2=2

Hope this helps-----ptaylor