2. Questions Bank
  3. 9th Class
  4. Mathematics
  5. Linear Equations in Two Variables

9th Class Mathematics Linear Equations in Two Variables Question Bank Linear Equations in Two Variables

  • question_answer
    Two planes start from a city and fly in opposite directions, one averaging a speed of \[40\] km/hour greater than the second. If they are \[3400\,\,km\] apart from \[5\] hours, find the sum of their average speeds.

    A) \[680\,\,km/h\]

    B)                    \[360\,\,km/h\]               

    C) \[320\,\,km/h\]   

    D)        \[640\,\,km/h\]

    Correct Answer: A

    Solution :

    Let the speed of one plane be \[x\]km/hour, Then the speed of other plane is \[(x+40)\,km/hour.\] Distance travelled by first plane in 5 hours = \[Speed\times Time=x\times 5=5x\] Distance travelled by second plane in \[5\,\text{hours}=(x+40)5.\] Distance travelled by first plane + Distance travelled by the other plane = 3400 km \[5x+5(x+40)=3400\] \[\Rightarrow \]\[x=\frac{3200}{10}=320km/\text{hour}\] Sum of speeds = (320 + 360) km/h = 680 km/hour


You need to login to perform this action.
You will be redirected in 3 sec spinner