Question

last month
pauls business cell phone charges for one month.
(a) the bill shows a total amount due of $158.88,
this includes charges of $38.88.
what percentage of the total amount are the charges?
(b) the previous months charge was $207.86 incl gst.
what is the gst exclusive price of last months charges?
(c) the current total charge is $158.88. the previous total charge was $207.86.
calculate the percentage change in pauls cell phone charge from the previous months charge.

Explanation:

Step1: Calculate percentage for (a)

For percentage formula: $\text{Percentage}=\frac{\text{Part}}{\text{Whole}}\times100$. Here, part is $38.88$ and whole is $158.88$.
$$\frac{38.88}{158.88}\times100=\frac{3888}{158.88}\approx24.47\%$$

Step2: Calculate GST - exclusive charge for (b)

Let the GST - exclusive charge be $x$. If $x(1 + 0.1)=207.86$ (assuming GST rate is $10\%$). Then $x=\frac{207.86}{1.1}=188.96$

Step3: Calculate percentage change for (c)

Percentage change formula: $\text{Percentage change}=\frac{\text{New}-\text{Old}}{\text{Old}}\times100$. New is $207.86$ and Old is $158.88$.
$$\frac{207.86 - 158.88}{158.88}\times100=\frac{48.98}{158.88}\times100\approx30.83\%$$

Answer:

(a) Approximately $24.47\%$; (b) $\$188.96$; (c) Approximately $30.83\%$