SOLUTION: Ndiba left the mall and traveled toward the lake. Two hours later Emily left traveling at 70 km/h in an effort to catch up to Ndiba. After traveling for three hours Emily finally c

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Question 1122487: Ndiba left the mall and traveled toward the lake. Two hours later Emily left traveling at 70 km/h in an effort to catch up to Ndiba. After traveling for three hours Emily finally caught up. What was Ndiba's average speed.
Found 2 solutions by ikleyn, josmiceli:
Answer by ikleyn(52858) About Me  (Show Source):
You can put this solution on YOUR website!
.
Emily traveled 3 hours at 70 km/h and covered the distance of  3*70 = 210 kilometers.


Ndiba traveled the same distance of 210 kilometers in 2 + 3 = 5 hours.


Hence, Ndiba's average speed was  210%2F5 = 42 kilometers per hour.

Solved.


Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +s+ = Ndiba’s average speed
+s%2A2+ = distance Ndiba travels before Emily leaves
Let +d+ = distance Emily travels until they meet
—————————
Neiba’s equation:
(1) +d+-+2s+=+s%2A3+
Emily’s equation:
(2) +d+=+70%2A3+
—————————
(1) +d+=+5s+
And
(2) +5s+=+70%2A3+
(2) +s+=+42+
—————————
Ndiba’s average speed is 42 km/hr
Check:
In 1st 2 hrs N traveled +s%2A2+=+84+ km
In next 3 hrs she traveled +s%2A1+=+126+ km
+84+%2B+126+=+210+ which was Emily’s distance
Since +d+=+70%2A3+
Get 2nd opinion if needed