Dom is a student. He has to write an essay for his
homework. The table shows how long it will
take him to do each stage of the essay. Unfortunately, Dom has left his
homework until the day before it is due. So he has to complete it today. He starts the essay at four pm. Dom’s friends have asked him to
play video games with them at nine pm. Will Dom complete his essay in time
to play video games with his friends at 9 pm?
We know that Dom starts his essay
at four pm. And he would like to join his
friends at 9 pm to play video games. We’ll need to calculate the length
of time it will take for Dom to complete his essay.
We can add a third column to the
table. This column represents the
cumulative time, in other words, the total time that Dom has taken since starting
his essay. We know that it takes 10 minutes to
plan the essay. So the first value that goes in
this column is 10.
It takes three-quarters of an hour
to complete the introduction. Since there are 60 minutes in one
hour, we can work out three-quarters of 60 to find the number of minutes he spends
completing the introduction. One-quarter of 60 is found by
dividing 60 by four. We can divide by four by halving
and then halving again. That’s the same as dividing by two
and then dividing by two again.
Half of 60 is 30 and half of 30 is
15. So one-quarter of 60 is 15. And since we want three-quarters,
we can multiply the value for one-quarter which was 15 by three. 15 multiplied by three is 45. So three-quarters of an hour is the
same as 45 minutes. He has taken 10 minutes to do the
planning and then 45 minutes to do the introduction. That means up to this point he’s
taking a total of 55 minutes.
Next, it takes him two and a
quarter hours to complete the main body. We already said that one-quarter of
an hour is 15 minutes and that one hour is equal to 60 minutes. Two and a quarter hours can be
found by adding 60 and 60 and 15. 60 plus 60 plus 15 is 135. So the total time taken so far can
be found by adding 55 and 135 to get 190 minutes.
It takes Dom 25 minutes to write
the conclusion. So we can add 190 to 25. And that gives us a total of 215
minutes through to writing the conclusion.
Finally, it takes one hour and five
minutes to review his work. Since one hour is 60 minutes, one
hour and five minutes is 65 minutes. 215 plus 65 is 280 minutes. Since he started his work at four
pm, we’ll need to change this into hours to find the time that he finishes.
Since 60 minutes is equal to one
hour, this time we’ll divide 280 by 60. Four multiplied by 60 is 240. So 280 divided by 60 is four
remainder 40. That means that it took him a total
of four hours and 40 minutes to complete his essay.
Since he started his essay at four
pm and it takes four hours and 40 minutes, he will be finished at 8:40 pm. So that’s plenty of time to meet
Remember it’s really important that
we make it clear we understand that this is in the evening. We either have to write 8:40 pm or
we write it in terms of the 24-hour clock; that’s 20:40.