An aircraft 200 kilometers away is flying toward an air base

An aircraft 200 kilometers away is flying toward an air base at 350 kilometers. How long will it take a plane flying from the base at 450 kilmeters per hour to interecept the first aircraft?

Solution

Distance(d) equals Rate(r) times Time(t) or d=rt; r=d/t and t=d/r (Note: these are givens--basic definitions. You don\'t need to figure these out but they should make sense)
Let t=time it takes the plane flying from base to intercept the first acft.
Now we know that when the distance the first plane flies plus the distance the second plane flies equals 200 km, the second plane will have intercepted the first plane. (In other words, they will be together.)
Distance first plane flies=350t (r*t)
Distance second plane flies=450t
So, our equation to solve is:
350t+450t=200 or
800t=200 divide both sides by 800
t=1/4 hr------------------------------answer
CK
In 1/4 hr, first plane travels 350*(1/4)=87.5 km
In 1/4 hr, second plane travels 450*(1/4)=112.5 km
87.5+112.5=200
200=200

Also, we know that the planes are approaching each other at the rate of 350+450 km/hr