1. Which of the following number is divisible by 24 ?
A. 35718
B. 63810
C. 537804
D. 3125736
E. 537805
2. [latex]\frac {753 \times 753 + 247 \times 247 - 753 \times 247}{753 \times 753 \times 753 + 247 \times 247 \times 247} = ?[/latex]
A. [latex]\frac {1}{1000}[/latex]
B. [latex]\frac {1}{506}[/latex]
C. [latex]\frac {253}{500}[/latex]
D. [latex]\frac {450} {500}[/latex]
E. None of these
3. (?) + 3699 + 1985 - 2047 = 31111
A. 34748
B. 27474
C. 30154
D. 27574
E. None of these
4. At 3:40, the hour hand and the minute hand of a clock form an angle of:
A. 120°
B. 125°
C. 130°
D. 135°
E. None of these
5. How many times are the hands of a clock at right angle in a day?
A. 22
B. 24
C. 44
D. 48
E. 50
Answers and Explanations
1. Answer - Option D
Explanation -
24 = 3 x 8, where 3 and 8 co-prime.
Clearly, 35718 is not divisible by 8, as 718 is not divisible by 8.
Similarly, 63810 is not divisible by 8 and 537804 is not divisible by 8.
Consider option (D),
Sum of digits = (3 + 1 + 2 + 5 + 7 + 3 + 6) = 27, which is divisible by 3.
Also, 736 is divisible by 8.
i.e, 3125736 is divisible by (3 x 8), i.e., 24.
2. Answer - Option A
Explanation -
[latex]\frac {{a}^{2} + {b}^{2} - ab}{{a}^{3} + {b}^{3}}= \frac {1}{a + b} = \frac {1}{753 + 247} = \frac {1}{1000}[/latex]
3. Answer - Option B
Explanation -
x + 3699 + 1985 - 2047 = 31111
[latex]\Rightarrow [/latex] x + 3699 + 1985 = 31111 + 2047
[latex]\Rightarrow [/latex] x + 5684 = 33158
[latex]\Rightarrow [/latex] x = 33158 - 5684 = 27474.
4. Answer - Option C
Explanation -
Angle traced by hour hand in 12 hrs. = 360°.
Angle traced by it in [latex]\frac {11}{3} hrs = (\frac {360}{12} \times \frac {11}{3})° = 110° [/latex]
Angle traced by minute hand in 60 min. = 360°.
Angle traced by it in 40 min. = [latex](\frac {360}{60} \times 40)° = 240°[latex]
i.e, Required angle (240 - 110)° = 130°
5. Answer - Option C
Explanation -
In 12 hours, they are at right angles 22 times.
i.e, In 24 hours, they are at right angles 44 times.