Profit = 10%

Marked price is same as the list price.
20% discount means that on RS. 100 (MP), the discount is RS. 20.
By unitary method, on RS.1 the discount will be RS. \(\frac{20}{100}\)
On RS. 220, discount = RS. \(\frac{20}{100} \times 220=\ Rs. 44\)
The sale price = (RS. 220 – RS. 44) or RS. 176
Rehana found the sale price like this —
A discount of 20% means for a MP of RS. 100, discount is RS. 20. Hence the sale price is RS. 80. Using unitary method, when MP is RS. 100, sale price is RS. 80;
When MP is RS. 1, sale price is RS.\(\frac{80}{100}\)
Hence when MP is RS. 220, sale price = RS. \(\frac{80}{100} \times 220=\text { RS. } 176\)

Discount = Marked Price – Sale Price
= RS. 840  – RS. 714
= RS. 126
Since discount is on marked price, we will have to use marked price as the base.
On marked price of RS. 840, the discount is RS. 126.
\(\text { Discount }=\frac{126}{840} \times 100 \%=15 \%\)

Rahul

40%

2:3

Marked price of the monitor = Rs 15600
Sales price of the monitor = Rs 12480
\(\therefore\)Discount = [Marked price] - [Sales price]
= Rs 15600 - Rs 12480 = Rs3120
\(\therefore\)Discount per cent = \(3120\over 15600\)x 100% = 20%

The price of the calculator = Rs 750
Sales tax = 5% of Rs750
\(=Rs {5\over100}\times 750=Rs{75\over2}=Rs37.5\)
\(\therefore\)Bill amount = Sales Price + Sales Tax
=Rs 750 + Rs 37.5 = Rs 787.5

Marked price of the shirt = Rs 850
Selling price of the shirt = Rs 765
\(\therefore\) Discount = [Marked price] - [Selling price]
= Rs 850 - Rs 765 = Rs 85
Now, d.iscount per cent =\({85\over 850}\times 100\%=10\%\)

Rs 364

Total amount payable by Ankit
= 550 + 5% of cost price
= 550 + \(\frac{5}{100}\times 550\)
= \(550+\frac{55}{2}=\frac{1100+55}{2}\) = Rs 577.5

∵ \(\frac{7}{3}\)% of the number = 147
⇒ \(\frac{7}{300}\)ｘNumber = 147
∴ Number = 147ｘ\(\frac{300}{7}\)= 6300

Here, time period (T) =  1\(\frac{1}{2}\)yr = \(\frac{3}{2}\)yr and rate = 8%
For half-yearly, time period, T =\(\frac{3}{2}\)ｘ2 = 3
and rate = \(\frac{8}{2}\)% = 4 %

Given, P = Rs 1200000, R = 3% per annum and n =3 yr
∴ A = P\((1+\frac{R}{100})^{n}\)= 1200000\((1+\frac{3}{100})^{3}\)=1200000\((\frac{103}{100})^{3}\)= 1200000ｘ\((\frac{103}{100})\)ｘ\((\frac{103}{100})\)ｘ\((\frac{103}{100})\)
= 1311272 (approx).
Hence, the population of the city will be 1311272 after three years.

Here, time period (T) = 3 yr and rate = 6% for half-yearly
∴ Time period (T) = 3 x 2 = 6 and rate =\(\frac{6}{2}\)% = 3%