Question
The table below shows the distance travelled by two vehicles A and B during each second :
Which vehicle is ahead at the end of $7^{th}$ second and by how much?
| Time $(s)$ | $0$ | $1$ | $2$ | $3$ | $4$ | $5$ | $6$ | $7$ |
| Distance travelled by $A (m)$ | $0$$ | $20$ | $80$ | $180$ | $240$ | $300$ | $360$ | $420$ |
| Distance travelled by $B (m)$ | $0$ | $10$ | $40$ | $90$ | $160$ | $250$ | $360$ | $490$ |