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11
0.04 x 0.0162 is equal to:
Discuss
Answer & Solution
Answer: Option B
Solution:
4 x 162 = 648. Sum of decimal places = 6.
So,
0.04 x 0.0162
= 0.000648
= 6.48 x 10-4
12
$$\frac{{4.2 \times 4.2 - 1.9 \times 1.9}}{{2.3 \times 6.1}}$$    is equal to:
Discuss
Answer & Solution
Answer: Option B
Solution:
$$\eqalign{ & \text{Let } a = 4.2 \text{ and } b = 1.9 \cr & {\text{Given Expression}} \cr & = \frac{{ {{a^2} - {b^2}} }}{{\left( {a + b} \right)\left( {a - b} \right)}} \cr & = \frac{{ {{a^2} - {b^2}} }}{{ {{a^2} - {b^2}} }} \cr & = 1 \cr} $$
13
If $$\frac{{144}}{{0.144}} = \frac{{14.4}}{x},$$   then the value of x is:
Discuss
Answer & Solution
Answer: Option A
Solution:
$$\eqalign{ & \frac{{144}}{{0.144}} = \frac{{14.4}}{x} \cr & \Rightarrow \frac{{144 \times 1000}}{{144}} = \frac{{14.4}}{x} \cr & \Rightarrow x = \frac{{14.4}}{{1000}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\, = 0.0144 \cr} $$
14
The price of commodity X increases by 40 paise every year, while the price of commodity Y increases by 15 paise every year. If in 2001, the price of commodity X was Rs. 4.20 and that of Y was Rs. 6.30, in which year commodity X will cost 40 paise more than the commodity Y ?
Discuss
Answer & Solution
Answer: Option B
Solution:
Suppose commodity X will cost 40 paise more than Y after z years
Then,(4.20 + 0.40z) − (6.30 + 0.15z) = 0.40
⇒ 0.25z = 0.40 + 2.10
$$\eqalign{ & \Rightarrow z = \frac{{2.50}}{{0.25}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{250}}{{25}} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\, = 10 \cr} $$
∴ X will cost 40 paise more than Y 10 years
After 2001 i.e., 2011
15
Which of the following are in descending order of their value ?
Discuss
Answer & Solution
Answer: Option D
Solution:
Converting each of the given fractions in to decimal form, we get
$$\eqalign{ & \frac{1}{3} = 0.33 \cr & \frac{2}{5} = 0.4 \cr & \frac{3}{7} = 0.42 \cr & \frac{4}{5} = 0.8 \cr & \frac{5}{6} = 0.83 \cr & \frac{6}{7} = 0.85 \cr} $$
Clearly, 0.85 > 0.83 > 0.8 > 0.42 > 0.4 > 0.33
So, $$\frac{6}{7}$$ > $$\frac{5}{6}$$ > $$\frac{4}{5}$$ > $$\frac{3}{7}$$ > $$\frac{2}{5}$$ > $$\frac{1}{3}$$
16
Which of the following fractions is greater than $$\frac{{3}}{{4}}$$ and less than $$\frac{{5}}{{6}}$$ ?
Discuss
Answer & Solution
Answer: Option C
Solution:
$$\eqalign{ & \frac{3}{4} = 0.75,{\kern 1pt} \cr & \frac{5}{6} = 0.833,{\kern 1pt} \cr & \frac{1}{2} = 0.5, \cr & \frac{2}{3} = 0.66, \cr & {\kern 1pt} \frac{4}{5} = 0.8, \cr & \frac{9}{{10}} = 0.9 \cr} $$
Clearly, 0.8 lies between 0.75 and 0.833
$$\therefore \frac{4}{5}{\text{lies between}}\frac{3}{4}{\text{and}}\frac{5}{6}$$
17
The rational number for recurring decimal 0.125125.... is:
Discuss
Answer & Solution
Answer: Option C
Solution:
$$0.125125... = 0.\overline {125} = \frac{{125}}{{999}}$$
18
617 + 6.017 + 0.617 + 6.0017 = ?
Discuss
Answer & Solution
Answer: Option C
Solution:
$$\eqalign{ & 617.00 \cr & \,\,\,\,\,\,\,6.017 \cr & \,\,\,\,\,\,\,0.617 \cr & + \,\,\,6.0017 \cr & - - - - - - \cr & \,\,\,629.6357 \cr & - - - - - - \cr} $$
19
The value of $$\frac{{489.1375 \times 0.0483 \times 1.956}}{{0.0873 \times 92.581 \times 99.749}}$$     is closest to:
Discuss
Answer & Solution
Answer: Option B
Solution:
$$\eqalign{ & \frac{{489.1375 \times 0.0483 \times 1.956}}{{0.0873 \times 92.581 \times 99.749}} \approx \frac{{489 \times 0.05 \times 2}}{{0.09 \times 93 \times 100}} \cr & = \frac{{489}}{{9 \times 93 \times 10}} \cr & = \frac{{163}}{{279}} \times \frac{1}{{10}} \cr & = \frac{{0.58}}{{10}} \cr & = 0.058 \approx 0.06 \cr} $$
20
0.002 x 0.5 = ?
Discuss
Answer & Solution
Answer: Option B
Solution:
2 x 5 = 10.
Sum of decimal places = 4
∴ 0.002 x 0.5 = 0.001