SSC JE Electrical Engineering 2014 Set 2 Paper

Question : 34 of 200

Marks: +1, -0

If 7x – 5y = 20 and 12x + 5y = 75, what is the value of xy ?

Solution:

7x – 5y = 20

...(i)

12x + 5y = 75

...(ii)
Adding equation (i) and (ii), we get

9x = 95

∴

x = 5

From equation (i)

35 – 5y = 20

5y = 15

∴ y = 3

Now

xy = 5 ×3 = 15

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