Math Problem Statement

how to doing 33 question?

When a number is divided by 14, 20 or 35, the remainder is always 3. Find the least possible value of the number.

Solution

Let's solve Question 33 step by step.

Problem:

You need to find the least possible value of a number that, when divided by 14, 20, or 35, always leaves a remainder of 3.

Step-by-Step Solution:

  1. Interpretation: If a number NN leaves a remainder of 3 when divided by 14, 20, or 35, this means: N3(mod14)N \equiv 3 \pmod{14} N3(mod20)N \equiv 3 \pmod{20} N3(mod35)N \equiv 3 \pmod{35} Essentially, N3N - 3 must be divisible by 14, 20, and 35.

  2. Find the Least Common Multiple (LCM): To find the least number that satisfies these conditions, calculate the LCM of 14, 20, and 35.

    • Prime factorization: 14=2×714 = 2 \times 7 20=22×520 = 2^2 \times 5 35=5×735 = 5 \times 7

    The LCM is the product of the highest powers of all prime factors: LCM=22×5×7=140\text{LCM} = 2^2 \times 5 \times 7 = 140

  3. Find the Least Value of the Number: The number N3N - 3 must be a multiple of the LCM, so: N3=140kfor some integer k.N - 3 = 140k \quad \text{for some integer } k. To get the smallest value of NN, choose k=1k = 1: N3=140N=140+3=143.N - 3 = 140 \quad \Rightarrow \quad N = 140 + 3 = 143.

Answer:

The least possible value of the number is 143.


Would you like any more details on this solution or have further questions?

Here are five related questions to deepen your understanding:

  1. How would the solution change if the remainder was 5 instead of 3?
  2. What is the prime factorization method, and how is it used to find the LCM?
  3. How can you use modular arithmetic to solve similar problems?
  4. How does finding the greatest common divisor (GCD) relate to finding the LCM?
  5. What if the numbers were larger? How would you approach the solution?

Tip:

When calculating the LCM of multiple numbers, always take the highest power of each prime factor involved.

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Math Problem Analysis

Mathematical Concepts

Number Theory
Modular Arithmetic
LCM (Least Common Multiple)

Formulas

LCM of numbers
Modular arithmetic: N ≡ r (mod m)

Theorems

LCM Theorem
Remainder Theorem

Suitable Grade Level

Grades 7-9