Class 10 Mathematics - Important Questions
Chapter 2: Numbers and Sequences (English Medium Solutions)
Overview
This document contains the step-by-step solutions for important Class 10 Chapter 2 (Numbers and Sequences) mathematics problems as explained in the YouTube lesson by Kalaimagal Academy.
Problem 1: Division & Word Problem (Euclid's Division Lemma)
Question: A man has 532 flower pots. He wants to arrange them in rows such that each row contains 21 flower pots. Find the number of completed rows and how many flower pots are left over.
Solution Steps:
- Total number of flower pots =
532 - Number of flower pots in each row =
21 - To find the completed rows and remaining pots, divide 532 by 21 using Euclid's Division Lemma:
a = bq + r, where0 ≤ r < b - Divide 532 by 21:
532 ÷ 21 = 25with a remainder of7532 = 21 × 25 + 7
• Number of completed rows = 25
• Remaining flower pots left over = 7
Problem 2: Prime Factorization (Example 2.10)
Question: If ab × ba = 800, find the values of a and b.
Solution Steps:
- Express 800 in terms of prime factors:
800 = 2 × 400
800 = 2 × 2 × 200
800 = 2 × 2 × 2 × 100
800 = 2 × 2 × 2 × 2 × 50
800 = 2 × 2 × 2 × 2 × 2 × 25
800 = 25 × 52 - Equating
ab × ba = 25 × 52:- Case 1:
a = 2andb = 5 - Case 2:
a = 5andb = 2
- Case 1:
Problem 3: Finding Exponents using Prime Factorization (Exercise 2.2, Q4)
Question: If 13824 = 2a × 3b, find the values of a and b.
Solution Steps:
- Perform prime factorization on 13824:
- Divide continuously by 2:
13824 ÷ 29 = 27 - Divide remainder by 3:
27 ÷ 33 = 1
- Divide continuously by 2:
- Therefore,
13824 = 29 × 33 - Comparing powers with
2a × 3b:a = 9b = 3
Problem 4: Modular Arithmetic - Congruence (Exercise 2.3, Q3)
Question: Find x such that 104 ≡ x (mod 19).
Solution Steps:
- Calculate
104 = 10,000 - We need to find the remainder x when 10,000 is divided by 19.
- Divide 10,000 by 19:
10000 = (19 × 526) + 6
- Remainder obtained =
6
Problem 5: Clock Arithmetic (Exercise 2.3, Q5)
Question: What is the time 100 hours after 7:00 AM?
Solution Steps:
- 1 day = 24 hours.
- Divide 100 hours by 24 to find full days and remaining hours:
100 ÷ 24 = 4 dayswith a remainder of4 hours(since24 × 4 = 96).
- After 4 full days (96 hours), the time will be 7:00 AM again.
- Add the remaining 4 hours to 7:00 AM:
7:00 AM + 4 hours = 11:00 AM
Problem 6: Calendar / Day Calculation
Question: Today is Tuesday. My uncle will come after 45 days. On which day will my uncle come?
Solution Steps:
- 1 week = 7 days.
- Divide 45 by 7 to find the number of completed weeks and leftover days:
45 ÷ 7 = 6 weekswith a remainder of3 days(since7 × 6 = 42).
- After 6 complete weeks (42 days), it will be Tuesday again.
- Count 3 days forward from Tuesday:
- Day 1: Wednesday
- Day 2: Thursday
- Day 3: Friday
Problem 7: Piecewise Defined Sequence (Example 2.21)
Question: Find the 11th and 18th terms of the sequence whose nth term is defined by:
an = n(n + 3) if n is odd
an = n2 + 1 if n is even
Solution Steps:
- To find a11 (since 11 is Odd):
- Use formula:
an = n(n + 3) a11 = 11 × (11 + 3) = 11 × 14 = 154
- Use formula:
- To find a18 (since 18 is Even):
- Use formula:
an = n2 + 1 a18 = 182 + 1 = 324 + 1 = 325
- Use formula:
Problem 8: Sequence Evaluation
Question: Find a8 and a15 for the sequence where:
an = (n2 - 1) / (n + 3) if n is even
an = n2 / (2n + 1) if n is odd
Solution Steps:
- To find a8 (since 8 is Even):
- Use formula:
an = (n2 - 1) / (n + 3) a8 = (82 - 1) / (8 + 3) = (64 - 1) / 11 = 63 / 11
- Use formula:
- To find a15 (since 15 is Odd):
- Use formula:
an = n2 / (2n + 1) a15 = 152 / (2(15) + 1) = 225 / (30 + 1) = 225 / 31
- Use formula:
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