Sister can bake 50 cakes in 25 hours, Sister and Mummy together can bake 75 cakes in 15 hours. How many cakes Mummy can bake in 15 hours ?

Number of cakes baked by sister in 1 hour

$=frac{50}{25}=2$

Number of cakes baked by mummy and sister in 1

hour

$=frac{75}{15}=5$

∴ Number of cakes baked by mummy in 1 hour

= 5 – 2 = 3

∴ Number of cakes baked by mummy in 15 hours

= 3 × 15 = 45