Math Problem Statement

a number being successively divided by 3, 5 and 8 leaves remainders 1, 4 and 7 respectively find the respective remainders if the order of divisors be reversed

Solution

Let's denote the number as NN. We are given the following conditions:

  1. NN when divided by 3 gives a remainder of 1.
  2. The quotient from the first division, when divided by 5, gives a remainder of 4.
  3. The quotient from the second division, when divided by 8, gives a remainder of 7.

Let's represent these conditions mathematically:

N=3a+1N = 3a + 1

Where aa is the quotient when NN is divided by 3.

Next, aa divided by 5 leaves a remainder of 4:

a=5b+4a = 5b + 4

Where bb is the quotient when aa is divided by 5.

Next, bb divided by 8 leaves a remainder of 7:

b=8c+7b = 8c + 7

Where cc is the quotient when bb is divided by 8.

Now, we substitute these equations back to find NN:

N=3a+1=3(5b+4)+1=15b+12+1=15b+13N = 3a + 1 = 3(5b + 4) + 1 = 15b + 12 + 1 = 15b + 13

Substitute b=8c+7b = 8c + 7 into the equation:

N=15(8c+7)+13=120c+105+13=120c+118N = 15(8c + 7) + 13 = 120c + 105 + 13 = 120c + 118

So the number NN can be expressed as:

N=120c+118N = 120c + 118

Reverse the Order of Divisors:

Now, if we reverse the order of divisors (8, 5, 3), we need to find the remainders when NN is divided by these divisors.

  1. First, divide by 8:

    N=120c+118N = 120c + 118 Nmod8=(120c+118)mod8N \mod 8 = (120c + 118) \mod 8

    Since 1200mod8120 \equiv 0 \mod 8 and 1186mod8118 \equiv 6 \mod 8:

    Nmod8=6N \mod 8 = 6

    So, the remainder when NN is divided by 8 is 6.

  2. Next, divide by 5:

    Let N1=6×(some integer)+6\text{Let } N_1 = 6 \times \text{(some integer)} + 6 We don't need the exact multiple; instead, we check N1mod5N_1 \mod 5:

    61mod56 \equiv 1 \mod 5

    So, the remainder when NN is divided by 5 is 3.

  3. Finally, divide by 3:

    Using the similar process: Nmod3=(120c+118)mod3N \mod 3 = (120c + 118) \mod 3

    1200mod3120 \equiv 0 \mod 3 and 1182mod3118 \equiv 2 \mod 3:

    So, the remainder when NN is divided by 3 is 2.

Conclusion:

The respective remainders when the divisors are reversed (8, 5, 3) are:

  • Remainder when divided by 8: 6
  • Remainder when divided by 5: 3
  • Remainder when divided by 3: 2

Would you like further details or explanations?

Related Questions:

  1. What is the general method to solve such remainder problems?
  2. How do the properties of congruences help in solving these problems?
  3. What are the uses of the Chinese Remainder Theorem in problems like this?
  4. How can you determine the original number NN using the conditions given?
  5. What would the remainders be if different divisors were used in reverse?
  6. Can you find NN using a direct approach without solving step by step?
  7. How does the order of operations affect the result?
  8. What are some common divisibility rules that might simplify problems like this?

Tip:

Understanding how congruences work and how they combine is crucial for solving complex remainder problems efficiently.

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Math Problem Analysis

Mathematical Concepts

Modular Arithmetic
Congruences

Formulas

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Theorems

Chinese Remainder Theorem

Suitable Grade Level

High School