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#### 3.7.47 Types Tutorial Exercise 15

The speed limit is 55 miles per hour on most highways. We want to find the ratio of Sam's speed to the US speed limit.

         1:  55 mph         2:  55 mph           3:  11 hr mph / yd
             .              1:  5 yd / hr            .
                                .

           ' 55 mph <RET>       ' 5 yd/hr <RET>          /

The `u s` command cancels out these units to get a plain number. Now we take the logarithm base two to find the final answer, assuming that each successive pill doubles his speed.

         1:  19360.       2:  19360.       1:  14.24
             .            1:  2                .
                              .

             u s              2                B

Thus Sam can take up to 14 pills without a worry.