Xavier planned to save $21 using his pocket money. The table below shows his saving plan for his weekly pocket money from Monday to Friday.

Day	Amount saved
Monday	$50\text{c}$
Tuesday	$50\text{c}$
Wednesday	$60\text{c}$
Thursday	$60\text{c}$
Friday	$80\text{c}$

Xavier started to save on a Friday. On which day of the week did Xavier managed to save exactly $21?

1. Calculate the total amount saved in one full week of saving (5 days).

$50 + 50 + 60 + 60 + 80 = 300\text{ c} = \char36{}3$

2. Find the number of full weeks needed to save exactly $21.

$\char36{}21 \div \char36{}3 = 7\text{ weeks}$

3. Determine the day of the week the 7th week ends on.

Since Xavier starts saving on a Friday, one full cycle of 5 saving days is Friday, Monday, Tuesday, Wednesday, and Thursday. The cycle ends on a Thursday. Since 7 weeks is an exact number of cycles, he will reach exactly $\char36{}21$ on a Thursday.