On the day of his 18th birthday, David decided to start saving money regularly.
a) Starting on that day, he could save £ 60 on the same date every month.
How much would he have saved by the day before his 60th birthday?
b) David explored another option.
Starting on his 18th birthday, he could save £ 100 on the same date every year.
If he saved in this way, how old would he be by the time he saved £ 2000?

The unitary method is a method for solving a problem by the first value of a single unit and then finding the value by multiplying the single value.

a) Let x be a number of months.

Now, we will find a number of years between 60 and 18 years.

There will be 42 years from 18th birthday to 60th birthday.

Now, we will convert 42 years into months.

42 × 12 = 504

In order to find the total amount saved in 504 months, we will substitute in expression:

30x = 30(504) = 15120

Hence, the person will save $15,120 by the day before his 60th birthday.

b) David starts saving £100 annually from his 18th birthday

We would save £2000 after

(2000/100) years = 20 years

Since his 18th birthday is the first of the 20 years and so he will save £950 for the next 19 years, which is

18 + 19 = 37 years old

Hence, David would have had £2000 when he is 37 years old.

Learn more about the unitary method;

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