A) 650 km/h
B) 360 km/h
C) 320 km/h
D) 640 km/h
Correct Answer: A
Solution :
(a): Let the speed of one plane be x km/hour. Then, the speed of other plane is \[\left( x+50 \right)\] km/hour. Distance travelled by first plane in 4 hours \[=\text{Speed}\times \text{Time}=x\times 4=4x\] Distance travelled by second plane in 4 hours \[=\left( x+50 \right)4.\] Distance travelled by first plane + Distance travelled by the other plane = 2600 km \[4x+4\left( x+50 \right)=2600\] \[\Rightarrow x=\frac{2400}{8}=300km/hour\] Sum of speeds \[=\left( 300+350 \right)km/h\] \[=650km/hour\]
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