121.
What is the unit digit in the product (365 x 659 x 771)?
A. 1 B. 2
C. 4 D. 6
Answer & Explanation
Answer: Option C
Explanation:
Unit digit in 34 = 1 Unit digit in (34)16 = 1
Unit digit in 365 = Unit digit in [ (34)16 x 3 ] = (1 x 3) = 3
Unit digit in 659 = 6
Unit digit in 74 Unit digit in (74)17 is 1.
Unit digit in 771 = Unit digit in [(74)17 x 73] = (1 x 3) = 3
Required digit = Unit digit in (3 x 6 x 3) = 4.
122.
3251 + 587 + 369 – ? = 3007
A. 1250 B. 1300
C. 1375 D. 1200
E. None of these
Answer & Explanation
Answer: Option D
Explanation:
3251 Let 4207 – x = 3007
+ 587 Then, x = 4207 – 3007 = 1200
+ 369
—-
4207
—-
123.
7589 – ? = 3434
A. 4242 B. 4155
C. 1123 D. 11023
E. None of these
Answer & Explanation
Answer: Option B
Explanation:
Let 7589 -x = 3434
Then, x = 7589 – 3434 = 4155
124.
217 x 217 + 183 x 183 = ?
A. 79698 B. 80578
C. 80698 D. 81268
Answer & Explanation
Answer: Option B
Explanation:
(217)2 + (183)2 = (200 + 17)2 + (200 – 17)2
= 2 x [(200)2 + (17)2] [Ref: (a + b)2 + (a – b)2 = 2(a2 + b2)]
= 2[40000 + 289]
= 2 x 40289
= 80578.
125.
The unit digit in the product (784 x 618 x 917 x 463) is:
A. 2 B. 3
C. 4 D. 5
Answer & Explanation
Answer: Option A
Explanation:
Unit digit in the given product = Unit digit in (4 x 8 x 7 x 3) = (672) = 2
126.
If the number 653 xy is divisible by 90, then (x + y) = ?
A. 2 B. 3
C. 4 D. 6
Answer & Explanation
Answer: Option C
Explanation:
90 = 10 x 9
Clearly, 653xy is divisible by 10, so y = 0
Now, 653×0 is divisible by 9.
So, (6 + 5 + 3 + x + 0) = (14 + x) is divisible by 9. So, x = 4.
Hence, (x + y) = (4 + 0) = 4.
127.
3897 x 999 = ?
A. 3883203 B. 3893103
C. 3639403 D. 3791203
E. None of these
Answer & Explanation
Answer: Option B
Explanation:
3897 x 999 = 3897 x (1000 – 1)
= 3897 x 1000 – 3897 x 1
= 3897000 – 3897
= 3893103.
128.
What is the unit digit in 7105 ?
A. 1 B. 5
C. 7 D. 9
Answer & Explanation
Answer: Option C
Explanation:
Unit digit in 7105 = Unit digit in [ (74)26 x 7 ]
But, unit digit in (74)26 = 1
Unit digit in 7105 = (1 x 7) = 7
129.
Which of the following numbers will completely divide (461 + 462 + 463 + 464) ?
A. 3 B. 10
C. 11 D. 13
Answer & Explanation
Answer: Option B
Explanation:
(461 + 462 + 463 + 464) = 461 x (1 + 4 + 42 + 43) = 461 x 85
= 460 x (4 x 85)
= (460 x 340), which is divisible by 10.
130.
106 x 106 – 94 x 94 = ?
A. 2400 B. 2000
C. 1904 D. 1906
E. None of these
Answer & Explanation
Answer: Option A
Explanation:
106 x 106 – 94 x 94 = (106)2 – (94)2
= (106 + 94)(106 – 94) [Ref: (a2 – b2) = (a + b)(a – b)]
= (200 x 12)
= 2400.