. On a circular highway, one has to pay toll charges at three places. In clockwise
order, they are a bridge which costs $1 to cross, a tunnel which costs $3 to pass
through, and the dam of a reservoir which costs $5 to go on top. Starting on the
highway between the dam and the bridge, a car goes clockwise and pays
toll-charges until the total bill amounts to $130. How much does it have to pay
at the next place?
【Solution】
Since 1+3+5=9, it takes $9 to go once around the highway. When 130 is divided by 9,
the quotient is 14, but more importantly the remainder is 4. This means that after
completing a number of round which happens to be 14, the car has pay an extra $4,
which means it has crossed the bridge and passed through the tunnel. At the next
place, it will have to pay $5 to go on top of the dam of the reservoir.
ANS: $5