Elementor #6127

Chapter 4: Expressions Using Letter-Numbers | Solutions

Chapter 4: Expressions Using Letter-Numbers

Complete solutions to all 10 reasoning questions, with correct options, formulas and step-by-step explanations.

Complete Answer Key

Question Option Correct Answer
1Cc x b A a
2C800 units
3D11
4C11 years
5A4 values
6A108 years
7C3
8C38
9B39
10BSunday

Question 1: Coded Mathematical Symbols

Given:
x means greater than (>)
$ means equal to (=)
< means not less than (≥)
A means less than (<)
+ means not greater than (≤)

Find the expression equivalent to a x b A c.

A. a $ c A b
B. b < a x c
C. c x b A a
D. c + b < a

Correct Answer: Option C — c x b A a

Step-by-Step Solution

  1. Replace each coded symbol with its meaning.
  2. The first comparison, a x b, means a > b.
  3. The second comparison, b A c, means b < c.
  4. Therefore, b is smaller than both a and c.
  5. We can write the same relationship as c > b < a.
  6. Converting it back into coded symbols gives c x b A a.
a > b < c   =   c > b < a

Final Answer: Option C.

Question 2: Factory Pipeline Distribution

A factory supplies goods to four cities through pipelines. The cities consume exactly the amount they require. If 300 units travel from City A to City B, how many units travel from City D to City B?

A. 200 units
B. 600 units
C. 800 units
D. 1000 units

Correct Answer: Option C — 800 units

Step-by-Step Solution

  1. City B requires 400 units for its own consumption.
  2. City C requires another 700 units, supplied through City B.
  3. So City B needs 400 + 700 = 1100 units.
  4. City A already sends 300 units to City B.
  5. The remaining units must arrive from City D.
1100 − 300 = 800 units

Therefore, the pipeline from D to B must carry 800 units.

Question 3: Letter-Number Substitution

Six letters A, B, C, P, Q and R represent six different numbers from the set {1, 2, 4, 5, 7, 9}.

Conditions:
A and C are consecutive and A > C.
P + Q = R and P > Q.
B is greater than both A and C.

Find:
(4P + 3B) − (2P + 3C) + (2A − 3B)

A. 9
B. 13
C. 15
D. 11

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Correct Answer: Option D — 11

Step-by-Step Solution

Step 1: Simplify the expression.

4P + 3B − 2P − 3C + 2A − 3B

The positive and negative 3B terms cancel.

= 2P + 2A − 3C

Step 2: Determine the numbers.

The only consecutive numbers in the given set are 1 and 2, so A = 2 and C = 1.

From the remaining numbers, 5 + 4 = 9. Because P > Q, we get P = 5, Q = 4 and R = 9.

The remaining number is 7, so B = 7.

Letter Value
A2
B7
C1
P5
Q4
R9

Step 3: Substitute.

2(5) + 2(2) − 3(1)
= 10 + 4 − 3
= 11

Final Answer: 11 (Option D).

Question 4: Maximum Possible Age

The sum of the ages of A, B, C and D is 35 years. Each person is at least 8 years old. What is the maximum possible age of the oldest person?

A. 9 years
B. 10 years
C. 11 years
D. 12 years

Correct Answer: Option C — 11 years

Step-by-Step Solution

  1. The total of all four ages is 35 years.
  2. Each individual must be at least 8 years old.
  3. To maximise one person's age, make the other three exactly 8 years old.
  4. The sum of those three ages is 8 + 8 + 8 = 24.
  5. Subtract 24 from the total of 35.
35 − 24 = 11 years

The oldest person can be a maximum of 11 years old.

Question 5: Possible Values of C

Three whole numbers A, B and C satisfy the following conditions:

A > B > C
A + B = 10

At maximum, how many different values can C have?

A. 4
B. 5
C. 3
D. 2

Correct Answer: Option A — 4 possible values

Step-by-Step Solution

  1. A, B and C are whole numbers.
  2. A must be greater than B, and B must be greater than C.
  3. The sum of A and B is 10.
  4. The largest possible B is 4, because A must still be larger.
  5. Therefore, choose A = 6 and B = 4.
  6. C can be any whole number smaller than 4.
C = 0, 1, 2, 3
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There are 4 possible values. Remember that zero is a whole number.

Question 6: Sum of Ages After 36 Years

The sum of the ages of Shubham and Shivam is 36 years. What will be the sum of their ages after 36 years?

A. 108
B. 136
C. 72
D. 96

Correct Answer: Option A — 108 years

Step-by-Step Solution

  1. The present sum of their ages is 36.
  2. After 36 years, Shubham will be 36 years older.
  3. Shivam will also be 36 years older.
  4. The total age increases by 72 years.
36 + 36 + 36 = 108

Therefore, their combined age after 36 years will be 108 years.

Question 7: Natural Number Relationships

A, B and Z are natural numbers.

A + B = Z
B = 2A
B > 4
Z < 10

Find the possible value of A.

A. 1
B. 2
C. 3
D. 4

Correct Answer: Option C — 3

Step-by-Step Solution

Given:

A + B = Z
B = 2A

Substituting B gives:

A + 2A = Z
3A = Z

We know B is greater than 4.

2A > 4
A > 2

We also know Z is less than 10.

3A < 10
A < 10/3

The only natural number greater than 2 and less than 10/3 is 3.

A = 3, B = 6, Z = 9

Final Answer: 3 (Option C).

Question 8: Number Pyramid

Each number in the pyramid equals the sum of the two numbers immediately below it. Find the value of P × Q + R.
14 Q R 1 P 3

A. 42
B. 48
C. 38
D. 36

Correct Answer: Option C — 38

Step-by-Step Solution

From the number pyramid:

Q = 1 + P
R = P + 3

The top number is 14.

Q + R = 14

Substitute the expressions for Q and R.

(1 + P) + (P + 3) = 14
2P + 4 = 14
2P = 10
P = 5

Therefore:

Q = 1 + 5 = 6
R = 5 + 3 = 8

Now calculate the required expression.

P × Q + R
= 5 × 6 + 8
= 30 + 8
= 38

Final Answer: 38 (Option C).

Question 9: Maximum Value of an Expression

5A, 5B and C9 are two-digit numbers. A, B and C represent digits.

A + B + C = 15
5A > 5B > C9

Find the maximum possible value of 3B + 4C + 8.

A. 43
B. 39
C. 31
D. 36

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Correct Answer: Option B — 39

Step-by-Step Solution

Step 1: Understand the inequality.

5A > 5B > C9

The numbers 5A and 5B both have 5 in the tens position. Therefore, A must be greater than B.

The number C9 is smaller than 5B. Therefore, C cannot exceed 4.

Step 2: Use the largest C.

C = 4
A + B + 4 = 15
A + B = 11

Since A must be greater than B, choose A = 6 and B = 5.

Step 3: Verify the numbers.

56 > 55 > 49

The condition is satisfied.

Step 4: Calculate the expression.

3B + 4C + 8
= 3(5) + 4(4) + 8
= 15 + 16 + 8
= 39

Smaller feasible values of C cannot produce a result above 39 while satisfying all the given conditions.

Final Answer: 39 (Option B).

Question 10: Calendar and Consecutive Multiples

In the given calendar, all marked dates are consecutive multiples of a particular number. The first marked date is the first Thursday. Determine the last day of the month.

A. Monday
B. Sunday
C. Saturday
D. Friday

Correct Answer: Option B — Sunday

Step-by-Step Solution

The marked dates occur on Thursday, Wednesday, Tuesday and Monday in successive weeks.

Moving from Thursday to Wednesday of the following week represents a gap of 6 days.

The marked dates must therefore be:

6, 12, 18, 24

Since the 6th is Thursday, the 1st is Saturday.

Calendar Illustration

Mon Tue Wed Thu Fri Sat Sun
12
345 6 X 789
1011 12 X 13141516
17 18 X 192021 2223
24 X 252627 282930

The 29th is Saturday, so the 30th falls on Sunday.

Last day of November = Sunday

Final Answer: Option B.

Final Answer Summary

Question Correct Option Answer
1Cc x b A a
2C800
3D11
4C11 years
5A4
6A108
7C3
8C38
9B39
10BSunday
Study Note: These worked solutions are based on Chapter 4, Expressions Using Letter-Numbers, questions 1 to 10. The explanations are written to help students understand the reasoning behind each correct answer.

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