I would like to ask about an answer to a logic question involving a bus service, shown below.
So I observed the bus stop at STATION and realised if it runs from 07:59 to 20:59, exactly 13 hours at 10 minute intervals, I calculated how many times a bus leaves station, which was
$$\frac{13 \times60}{10} = 78$$
and likewise from 20:45, where buses run every 15 minutes from STATION
$$\frac{2\times60}{15} = 8$$
So I thought the total number of services run was $78 + 8 = 86$ however I appear to be wrong. The answer is apparently $88$ but I can't seem to arrive to the answer of 88.
Can someone help see me where I went wrong?
Suppose a bus comes every $10$ minutes starting from $8$am until $9$ am, which is exactly $1$ hour. How manu buses come in $1$ hour.
Answer would be $7$.
At $8$am, $8:10$ am, $\ldots,8:50$ am, $9:00$am
Do not forget to count the bus at $8$am.