Question

Amy is 9 years older than her younger sister. if her younger sister is now 1 year old, how many years later will Amy be 4 times as old as her younger sister?​

Answer 1

Answer:-

• Age of Amy's younger sister=1year

☆Amy is 9 years older than her younger sister.

$\\ \sf\longmapsto Age\:of\:Amy=1+9=10years$

Let after x years Amy will be 4times old as her sister.

ATQ

$\\ \sf\longmapsto \dfrac{1+x}{9+x}=\dfrac{1}{4}$

• Using cross multiplication

$\\ \sf\longmapsto 4(1+x)=1(9+x)$

$\\ \sf\longmapsto 4+4x=9+x$

$\\ \sf\longmapsto 4x-x=9-4$

$\\ \sf\longmapsto 3x=5$

$\\ \sf\longmapsto x=\dfrac{5}{3}$

$\\ \sf\longmapsto x=1.6$

$\\ \sf\longmapsto x=2(approx)$