Numbers

Question:
(12345679 x 72) = ?

[A].

88888888

[B].

888888888

[C].

898989898

[D].

9999999998

Answer: Option B

Explanation:

12345679 x 72	= 12345679 x (70 +2)
	= 12345679 x 70 + 12345679 x 2
	= 864197530 + 24691358
	= 888888888

Question:
(935421 x 625) = ?

[A].

575648125

[B].

584638125

[C].

584649125

[D].

585628125

Answer: Option B

Explanation:

935421 x 625 = 935421 x 54 = 935421 x		10		4
		2

=	935421 x 104	=	9354210000
	24		16

= 584638125

Question:
(112 x 54) = ?

[A].

67000

[B].

70000

[C].

76500

[D].

77200

Answer: Option B

Explanation:

(112 x 54) = 112 x		10		4	=	112 x 104	=	1120000	= 70000
		2				24		16

Question:
{(476 + 424)2 – 4 x 476 x 424} = ?

[A].

2906

[B].

3116

[C].

2704

[D].

2904

Answer: Option C

Explanation:

Given Exp.	= [(a + b)2 – 4ab], where a = 476 and b = 424
	= [(476 + 424)2 – 4 x 476 x 424]
	= [(900)2 – 807296]
	= 810000 – 807296
	= 2704.

Question:
287 x 287 + 269 x 269 – 2 x 287 x 269 = ?

[A].

534

[B].

446

[C].

354

[D].

324

Answer: Option D

Explanation:

Given Exp.	= a2 + b2 – 2ab, where a = 287 and b = 269
	= (a – b)2 = (287 – 269)2
	= (182)
	= 324

Question:
The unit digit in the product (784 x 618 x 917 x 463) is:

[A].

2

[B].

3

[C].

4

[D].

5

Answer: Option A

Explanation:

Unit digit in the given product = Unit digit in (4 x 8 x 7 x 3) = (672) = 2

Question: 8796 x 223 + 8796 x 77 = ?

[A].

2736900

[B].

2638800

[C].

2658560

[D].

2716740

Answer: Option B

Explanation:

8796 x 223 + 8796 x 77	= 8796 x (223 + 77)   [Ref: By Distributive Law ]
	= (8796 x 300)
	= 2638800

Question:
106 x 106 – 94 x 94 = ?

[A].

2400

[B].

2000

[C].

1904

[D].

1906

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.

Question: 217 x 217 + 183 x 183 = ?

[A].

79698

[B].

80578

[C].

80698

[D].

81268

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.

Question: 107 x 107 + 93 x 93 = ?

[A].

19578

[B].

19418

[C].

20098

[D].

21908

Answer: Option C

Explanation:

107 x 107 + 93 x 93	= (107)2 + (93)2
	= (100 + 7)2 + (100 – 7)2
	= 2 x [(100)2 + 72]       [Ref: (a + b)2 + (a – b)2 = 2(a2 + b2)]
	= 20098