A sum of Rs. 625 is made up of 80 currency notes which are of either Rs. 10 or Rs. 5 denomination. The number of Rs. 10 notes are

Solution
Let the number of 10 rupee notes be X.
∴ Number of 5 rupee notes
= 80x
∴ (80x) x 5 + 10x= 625
⇒ 400  5x+ 1Ox = 625
⇒5x= 225
⇒X=^{225}⁄_{5}=45
On what sum of money will the compound interest for 3 years at 5%per annum amount to Rs.630.50 ?

Solution
\(CI=p\left [ \left ( 1+\frac{R}{100} \right )^{T}1 \right ]\)
\(\Rightarrow 630.50=p\left [ \left ( 1+\frac{5}{100} \right )^{3}1 \right ]\)
⇒630.50
\(=p\left ( \frac{261 8000}{8000 } \right )\)
\(\Rightarrow p=\frac{630.50 \times 8000}{1261}\)
= Rs. 4000
A sum of money put out at compound interest amounts to Rs. 16900 in 2 years and to Rs. 17576 in 3 years. Find the
rate of interest per annum.

Solution
Let the principal be Rs. P and rate of interest be R% p.a.
\(∴16900=P\left ( 1+\frac{R}{100} \right )^{2}.......(i)\)
\(\left [ A=p\left ( 1+\frac{R}{100} \right )^{T} \right ]\)
and 17576 = P\(\left ( 1+\frac{R}{100} \right )^{3}......(ii)\)
On dividing equation (ii)by (i),
\(\frac{17576}{16900 }=1+\frac{R}{100}\)
\(∴R=\frac{R}{100}=\frac{676}{16900}\times 100= 4%\)
Asum of money was invested at a certain rate for 2 years. Had it been invested at 3% higher rate of interest, it would have fetched Rs. 450 more. The sum invested was:

Solution
Let initial rate of interest be r% p.a. and principal be Rs. x. According to the question,
\(\frac{x \times (r + 3) \times 2 }{100}\frac{x \times r \times 2}{100}\)
= 450
\(\left [ S.I.=\frac{P\times R\times T}{100} \right ]\)\(\Rightarrow \frac{x\times 3\times 2}{100}=450\)
\(\Rightarrow x=\frac{450 \times 100}{6}= Rs. 7500\)
12 copies of a book were sold for Rs. 1800, thereby galning the cost price of 3 copies. The cost price of a copy is :

Solution
Let the CP of a copy be Rs. X.
∴ Gain = Rs. 3x
CP of 12 copies = Rs. 12x
∴ 1800  12x = 3x
⇒15x= 1800
∴ X=\(\frac{1800}{15}\)= Rs. 120
The cost price of 18 articles is equal to the selling price of 15 articles. The gain per cent is :

Solution
Let the CP of each article be Re. 1.
∴ CP of 15 articles = Rs. 15
SP of 15 articles = Rs. 18
∴ Gain = Rs. (18  15) = Rs. 3
∴ Gain per cent
= \(\frac{3}{15}\) × 100 = 20%
Who wrote the book, Never Gandhi Not Again ?

Solution
Omesh Saigal
Thomas Cup is associated with

Solution
Badminton
India’s maximum tax revenue comes from

Solution
Excise Tax
Prambikulam Dam has been an is sue of dispute between

Solution
Tamil Nadu and Kerala