Luxmi sold two sarees for ₹ 1980 each. On one, she lost 10%, while on the other she gained 10%. Find her gain or loss per cent in the whole transaction.
SP of first saree $=₹ 1,980$
Loss $=10 \%$
Let the CP of first saree be ₹ $x .$
CP $=$ Loss $+$ SP
$\Rightarrow \frac{10}{100} \times x+1980=x$
$\Rightarrow x-\frac{10}{100} x=1980$
$\Rightarrow \frac{90}{100} x=1980$
$\Rightarrow x=2200$
$\therefore$ CP of first saree $=$ ₹ 2,200
SP of second saree $=$ ₹ 1,980
Gain $=10 \%$
Let the CP of second saree be ₹ $y .$
CP $=$ SP $-$ Gain
$\Rightarrow 1980-\frac{10}{100} \times y=y$
$\Rightarrow 1980-\frac{y}{10}=y$
$\Rightarrow y+\frac{y}{10}=1980$
$\Rightarrow \frac{11 y}{10}=1980$
$\Rightarrow y=1800$
∴ CP of second saree = ₹1,800
Total CP of two sarees = CP of first saree + CP of second saree = ₹2,200 + ₹1,800 = ₹4,000
Total SP of two sarees = SP of first saree + SP of second saree = ₹1,980 + ₹1,980 = ₹3,960
Here, Total CP of two sarees > Total SP of two sarees
Loss = Total CP of two sarees − Total SP of two sarees = ₹4,000 − ₹3,960 = ₹40
$\therefore$ Loss $\%$ in the whole transaction $=\frac{\text { Loss }}{\text { Total CP of two sares }} \times 100 \%=\frac{40}{4000} \times 100 \%=1 \%$