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Question (1)

QN0029513

A student thinks of a number, triples it, subtracts 9, divides by 3 and finally subtracts the original number. What is always obtained?

(A) 0
(B) 3
(C) –3
(D) 9

Correct Answer: C

Explanation:

Let the number be x. Then (3x – 9)/3 = x – 3. Subtracting x gives –3.

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Question (2)

QN0029514

In a ‘Think of a Date’ trick, the final answer obtained is 970. If the same steps as in the chapter are followed, what was the date chosen?

(A) 5 August
(B) 5 September
(C) 10 August
(D) 15 July

Correct Answer: B

Explanation:

Final number = 100M + 165 + D. Thus, 970 – 165 = 805. Hence, M = 8 and D = 5, i.e., 5 September.

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Question (3)

QN0029515

The bottom row of a 3-row number pyramid is 6, 10, 14. What is the top number?

(A) 30
(B) 40
(C) 50
(D) 60

Correct Answer: B

Explanation:

In a 3-row pyramid, top = a + 2b + c = 6 + 2×10 + 14 = 40.

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Question (4)

QN0029516

The top of a 3-row number pyramid is 52. The bottom row contains 8, x, 12. Find x.

(A) 14
(B) 16
(C) 18
(D) 20

Correct Answer: B

Explanation:

Using top = a + 2b + c, we get 8 + 2x + 12 = 52. Therefore, x = 16.

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Question (5)

QN0029517

The bottom row of a 4-row pyramid is 1, 2, 3, 4. What is the topmost number?

(A) 15
(B) 18
(C) 20
(D) 24

Correct Answer: C

Explanation:

Filling the pyramid gives rows 3, 5, 7; then 8, 12; and finally 20 at the top.

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Question (6)

QN0029518

If the bottom row of a 3-row pyramid consists of three consecutive integers 9, 10, 11, then the top number is

(A) 39
(B) 40
(C) 41
(D) 42

Correct Answer: B

Explanation:

Top = 9 + 2×10 + 11 = 40.

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Question (7)

QN0029519

In a calendar, the sum of numbers in a 2 × 2 block is 64. What is the top-left number?

(A) 10
(B) 11
(C) 12
(D) 13

Correct Answer: C

Explanation:

If the top-left number is a, then the sum is 4a + 16. So, 4a + 16 = 64, giving a = 12.

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Question (8)

QN0029520

A friend selects a 2 × 2 calendar block whose top-left entry is 17. What is the sum of the four numbers?

(A) 76
(B) 80
(C) 84
(D) 88

Correct Answer: C

Explanation:

The numbers are 17, 18, 24 and 25. Their sum is 84.

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Question (9)

QN0029521

Which arrangement gives the largest product using digits 2, 6 and 8 exactly once?

(A) 86 × 2
(B) 68 × 2
(C) 62 × 8
(D) 82 × 6

Correct Answer: C

Explanation:

The largest digit should be used as the multiplier, and the remaining digits should be arranged in descending order. Hence, 62 × 8.

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Question (10)

QN0029522

Using digits 1, 4 and 9 exactly once, the largest possible product is

(A) 41 × 9
(B) 91 × 4
(C) 94 × 1
(D) 49 × 1

Correct Answer: A

Explanation:

The largest product is obtained by taking the largest digit as multiplier and arranging the other digits in descending order: 41 × 9.

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Question (1)

A student thinks of a number, triples it, subtracts 9, divides by 3 and finally subtracts the original number. What is always obtained?

Explanation:

Link:

Question (2)

In a ‘Think of a Date’ trick, the final answer obtained is 970. If the same steps as in the chapter are followed, what was the date chosen?

Explanation:

Link:

Question (3)

The bottom row of a 3-row number pyramid is 6, 10, 14. What is the top number?

Explanation:

Link:

Question (4)

The top of a 3-row number pyramid is 52. The bottom row contains 8, x, 12. Find x.

Explanation:

Link:

Question (5)

The bottom row of a 4-row pyramid is 1, 2, 3, 4. What is the topmost number?

Explanation:

Link:

Question (6)

If the bottom row of a 3-row pyramid consists of three consecutive integers 9, 10, 11, then the top number is

Explanation:

Link:

Question (7)

In a calendar, the sum of numbers in a 2 × 2 block is 64. What is the top-left number?

Explanation:

Link:

Question (8)

A friend selects a 2 × 2 calendar block whose top-left entry is 17. What is the sum of the four numbers?

Explanation:

Link:

Question (9)

Which arrangement gives the largest product using digits 2, 6 and 8 exactly once?

Explanation:

Link:

Question (10)

Using digits 1, 4 and 9 exactly once, the largest possible product is

Explanation:

Link:

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