Question

bananas are bought at rupees 10 per dozen and sold at Rupees 1 per banana then find gain or lost percent

Answer 1

there will be gain because when we buy 12 bananas for rs 10 and sell them at rs 12
so,
12-10=2
we gain 2 rs

Answer 2

1 dozen bananas are bought in 10 rupee
12 banana = 10/-
1 banana
$= \frac{10}{12} \\ 0.80 \: approx$

SP = 1 banana per 1 rupee
12 bananas = 12 rupee

loss = SP - CP
loss % =
$\frac{difference \: of \: amount}{cost \: price} \times 100$