Converting Time and Calculating Time

The units you need are seconds, minutes, hours and days: 60 seconds make 1 minute, 60 minutes make 1 hour, and 24 hours make 1 day. With those three facts you can change any time into another unit, multiplying to go to a smaller unit and dividing to go to a larger one.

Divide the minutes by 60, because there are 60 minutes in an hour and hours are the larger unit. So 120 minutes = 120 ÷ 60 = 2 hours, and 90 minutes = 1.5 hours, or 1 hour 30 minutes. For 45 minutes, 45 ÷ 60 = 0.75, so 45 minutes is 0.75 of an hour, three quarters.

Multiply the hours by 60, because each hour has 60 minutes and minutes are the smaller unit. So 2 hours = 2 × 60 = 120 minutes. For a time with both, convert the hours and add the minutes: 2 hours 15 minutes is 120 + 15 = 135 minutes.

Divide the seconds by 60, because every 60 seconds make 1 minute and minutes are the larger unit. So 300 seconds = 300 ÷ 60 = 5 minutes. Going the other way, from minutes to seconds, multiply by 60: 5 minutes = 300 seconds.

Add the minutes and the seconds separately. A cycling time of 35 min 20 s plus a running time of 20 min 45 s gives 55 minutes and 65 seconds. Since 65 seconds is more than 60, swap 60 seconds for 1 minute and keep the 5 seconds left over: the total is 56 minutes 5 seconds.

Subtract the minutes and the seconds separately. If the top seconds are smaller, borrow 1 minute and turn it into 60 seconds first. For 56 min 5 s minus 54 min 23 s: 5 is less than 23, so borrow a minute to get 55 min 65 s, then 65 − 23 = 42 seconds and 55 − 54 = 1 minute. The champion was 1 minute 42 seconds faster.