Class 8 Exam  >  Class 8 Questions  >  Joyce has between 25 and 75 coloured beads. W... Start Learning for Free
Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have?
Most Upvoted Answer
Joyce has between 25 and 75 coloured beads. When she makes them into g...
**Problem Analysis**

Let's represent the number of beads Joyce has as "x". We are given two conditions:

1. When Joyce makes groups of 9 beads, 8 beads are left out.
2. When Joyce makes groups of 8 beads, 6 beads are left out.

We can translate these conditions into equations:

1. x ≡ 8 (mod 9)
2. x ≡ 6 (mod 8)

Now, we need to find the value of "x" that satisfies both equations.

**Solving the Equations**

To solve these congruence equations, we can use the Chinese Remainder Theorem (CRT). CRT states that if we have a system of congruence equations:

x ≡ a (mod m)
x ≡ b (mod n)

where m and n are coprime (i.e., they have no common factors), then the solution is given by:

x ≡ (a * n * inv(n, m) + b * m * inv(m, n)) (mod m * n)

where inv(a, b) represents the modular multiplicative inverse of a modulo b.

In our case, m = 9 and n = 8. We need to find the modular inverses inv(9, 8) and inv(8, 9).

**Finding Modular Inverses**

To find the modular inverse inv(9, 8), we can use the Extended Euclidean Algorithm. The algorithm states that for any two integers a and b, there exist integers x and y such that:

a * x + b * y = gcd(a, b)

In our case, a = 9 and b = 8. We can apply the Extended Euclidean Algorithm to find x and y.

9 * x + 8 * y = gcd(9, 8)

By applying the algorithm, we find that x = -1 and y = 1. Since we are only interested in the modular inverse, we take the modulo of x and y by their respective moduli:

x ≡ -1 (mod 8)
y ≡ 1 (mod 9)

Therefore, inv(9, 8) = -1 (mod 8).

Similarly, applying the Extended Euclidean Algorithm to find inv(8, 9), we find inv(8, 9) = 8 (mod 9).

**Applying the Chinese Remainder Theorem**

Now that we have found the modular inverses, we can apply the Chinese Remainder Theorem formula to find the solution for "x":

x ≡ (8 * 8 * inv(8, 9) + 6 * 9 * inv(9, 8)) (mod 9 * 8)

Simplifying the expression, we get:

x ≡ (64 - 54) (mod 72)
x ≡ 10 (mod 72)

Therefore, the solution for "x" is x ≡ 10 (mod 72).

**Finding the Range of Possible Values for "x"**

Since we know that Joyce has between 25 and 75 colored beads, we can find the range of possible values for "x" within this range.

x ≡ 10 (mod 72)

We can write this congruence equation as:

x = 10 + 72k

where k is an integer.

Substit
Community Answer
Joyce has between 25 and 75 coloured beads. When she makes them into g...
50
Attention Class 8 Students!
To make sure you are not studying endlessly, EduRev has designed Class 8 study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Class 8.
Explore Courses for Class 8 exam

Top Courses for Class 8

Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have?
Question Description
Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have? for Class 8 2024 is part of Class 8 preparation. The Question and answers have been prepared according to the Class 8 exam syllabus. Information about Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have? covers all topics & solutions for Class 8 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have?.
Solutions for Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have? in English & in Hindi are available as part of our courses for Class 8. Download more important topics, notes, lectures and mock test series for Class 8 Exam by signing up for free.
Here you can find the meaning of Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have? defined & explained in the simplest way possible. Besides giving the explanation of Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have?, a detailed solution for Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have? has been provided alongside types of Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have? theory, EduRev gives you an ample number of questions to practice Joyce has between 25 and 75 coloured beads. When she makes them into groups of 9,8 beads are left out. When she groups them into groups of 8,6 beads are left out. How many beads does she have? tests, examples and also practice Class 8 tests.
Explore Courses for Class 8 exam

Top Courses for Class 8

Explore Courses
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev