⇒ Average = sum of elements / NUMBER of elements

Given,

Let the price of an orange and an apple be Rs. a and Rs. b.

Given,

The average price of 40 ORANGES is 80% of average price of 20 apples in a basket.

The average price of 40 oranges = (40 × a)/40 = a

The average price of 20 apples = (20 × b)/20 = b

⇒ a = (80/100) × b

⇒ a = 4b/5

⇒ b = 5a/4

Given,

The price of a pineapple is 40% of price of an orange.

Let the price of a pineapple be Rs. m.

⇒ a = (40/100) × m

⇒ a = 2m/5

⇒ m = 5a/2

Given,

a = Rs. 8

Then,

⇒ b = 5a/4 = (5 × 8)/4 = Rs. 10

⇒ m = 5a/2 = (5 × 8)/2 = Rs. 20

If 5 more pineapples are added into the basket of price Rs. 20 each then,

⇒ TOTAL price of 5 pineapples = 5 × 20 = Rs. 100

⇒ Total price of 40 oranges = 40 × 8 = Rs. 320

⇒ Total price of 20 apples = 20 × 10 = Rs. 200

Total price of 40 oranges, 20 apples and 5 pineapples in a basket =

= 100 + 320 + 200

= 620

Average price of a basket contains 40 oranges, 20 apples and 5 pineapples =

= 620/(40 + 20 + 5)

= 620/65

= 9.53

Average price of a basket contains 40 oranges, 20 apples and 5 pineapples is Rs. 9.53.

Alternate Solution: Price of an orange = 8

So, price of an apple will be = 10

And Price of a pineapple will be = 20

Average price of a fruit = (8 × 40 + 10 × 20 + 20 × 5)/65 = 620/65 = 9.53