Question

Solve 0.4x + 0.3y = 1.7; 0.7 x − 0.2y = 0.8

Answer 1

0.4x + 0.3y = 1.7

∴ 4x + 3y = 17 ......(i)[Multiplying both sides by 10]

0.7x – 0.2y = 0.8

∴ 7x – 2y = 8   ......(ii)[Multiplying both sides by 10]

Multiplying equation (i) by 2, we get

8x + 6y = 34     ......(iii)

Multiplying equation (ii) by 3, we get

21x – 6y = 24   ......(iv)

Adding equations (iii) and (iv), we get

    8x + 6y = 34
+21x – 6y = 24  
  29x         = 58

∴ x = `58/29` = 2

Substituting x = 2 in equation (i), we get

4(2) + 3y = 17

∴ 8 + 3y = 17

∴ 3y = 9

∴ y = `9/3` = 3

∴ x = 2 and y = 3 is the solution of the equation 0.4x + 0.3y = 1.7 and 0.7x – 0.2y = 0.8.