Solution:Let the price of the costliest bat = x
Let the price of the cheapest bat = y
Let the price of each of the 3 remaining bat = z
Average price of all 5 bats = 800 (given)
Total cost of all the five bats = Average × 5
⇒ 800 × 5 = 4000
⇒ x + y + z + z + z = 4000
⇒ x + y + 3z = 4000 ---- (I)
It is also given the price of the cheapest bat is a perfect square number and greater than 350 and less than 500
Possible values of y = 361, 400, 441, 484
The difference between the price of the costliest bat and the cheapest bat is
= 1700 (given)
⇒ x - y = 1700
Taking value of y = 361
⇒ x = y + 1700 ⇒ x = 361 + 1700
⇒ x = 2061
Putting values of x and y in (I)
⇒ 2061 + 361 + 3z = 4000
⇒ 3z = 4000 - 2462
⇒ 3z = 1538
⇒ z = 1538/3
⇒ z = 512.667
But the price of all the bats must be in whole numbers (given):
⇒ Value of y can’t be = 361
Taking value of y = 400
⇒ x = y + 1700
⇒ x = 400 + 1700
⇒ x = 2100
Putting values of x and y in (I)
⇒ 2100 + 400 + 3z = 4000
⇒ 3z = 4000 - 2100 - 400
⇒ 3z = 1500
⇒ z = 500
The value of z comes out to be = 500, which is a whole number
The price of each of the remaining 3 bats = Rs 500
The price of the costliest bat = Rs. 2100
The price of the cheapest bat = Rs. 400
No other value satisfies the option
∴ The price of the costliest bat = x = Rs. 2100