Question

If a person drives $126$ km in $3$ h, then find the distance travelled by him in $4$ h.

Answer 1

Three quantities, distance and time of one ratio and time of the second ratio, are given. Hence, the fourth quantity, i.e., distance of the second ratio, can be found using proportion since the two ratios $(speed=\frac{d}{t})$ are equal and, hence, proportional. Therefore,
$\frac{126}{3}=\frac{x}{4}$ (where x is the distance)
or $x=\frac{126\times 4}{3}=128km$