What costing Rs 35/kg, Rs 42/kg and a third variety of wheat are mixed in the ratio of 3 : 5 : 7.  If the mixture costs Rs 38/kg, then what will be the cost of the third variety of wheat?

36.42

ATQ, cost of wheat is:

I.     35 × 3 = 105 .... (i)

II.    42 × 5 = 210 ... (ii)

III.    R × 7 = 7R   ...(iii)

Equation (i) + (ii)

⇒ Total value of 1st and 2nd variety of wheat = 105 + 210 = 315

⇒ Total quantity = 15 Kg

Hence, total value of whole wheat = 15 × 38 = 570

⇒ Total value of 3rd variety of wheat = 570 - 315 = 255

Therefore,

⇒ Cost of 3rd variety of wheat = \(\frac{255}{7}\) = Rs.36.42 per kg