Question

Solve the following pairs of equations by cross multiplication method
$0.3x+0.4y=2.5\text{and}0.5x-0.3y=0.3$

Answer 1

Given equations are $0.3x+0.4y=2.5$......(i)

$0.5x-0.3y=0.3$........(ii)

Multiply equation (i) by 0.3 and (ii) by 0.4 and add them

$(0.3x+0.4y=2.5)\left(0.3\right)$

$(0.5x-0.3y=0.3)\left(0.4\right)$

$0.09x+0.12y=0.75$

$\underset{–}{0.2x-0.12y=0.12}$

$\underset{–}{0.29x=0.87}$

$x=\frac{0.87}{0.29}$

$x=3$

$\left(0.3\right)\left(3\right)+0.4y=2.5$

$0.4y=2.5-0.9$

$0.4y=1.6$

$y=4$

$x=3$ and $y=4$.