Question

Point A and B are $90$ km apart from each other on a highway. A car starts from A and another from B at the same time . If they go in the same direction they meet in $9$ hours and they go in opposite direction they meet in $9/7$ hours Find their speed.

Answer 1

when $A$ & $B$ were in same direction let they meet at $c$ which is $x$ km from $b$

$spee{d}_A=\frac{90+x}{9}$ km/hr

$spee{d}_A=\frac{x}{9}$ km/hr

when $A$ & $B$ were in opposite direction they take $9/7$ hr to meet

therefore distance cover by $A=\frac{90+x}{9}\times \frac{9}{7}$

$=\frac{90+x}{7}$ km

distance cover by $B=\frac{x}{9}\times \frac{9}{7}$

$=\frac{90+x}{7}+\frac{x}{7}=90$

$⟹90+2x=90\times 7$

$x=270$km

$S_A=40$ km/h $S_B=30$ km/h