Correct Answer - Option 1 : 10
GIven:
In 4\(\frac{1}{2}\) hours, Jack can cover a distance of 6 km more than the distance covered by Jill in 3 hours
In 6 hours, Jack can cover 5 km less than the distance covered by Jill in 5 hours
Concept used:
linear equations in two variables
Calculation:
Let the speed of Jack be x km/h and Jill be y km/h
9x/2 - 3y = 6 ----(i) × 4
⇒ 18x - 12y = 24 ----(iii)
5y - 6x = 5 ----(ii) × 3
⇒ 15y - 18x = 15 ----(iv)
By (iii) + (iv) we get
3y = 39
⇒ y = 13
9x/2 = 6 + 3 × 13
⇒ 9x = 45 × 2
⇒ x = 10
∴ Average speed of Jack is 10 km/h