Math Problem Statement

  1. Mod prods. Which number from 0 to 6 is equivalent to 16 mod 7? Whichnumber from 0 to 6 is equivalent to 24 mod 7? Which number from 0 to 6is equivalent to 16 × 24 mod 7? What number is equivalent to (16 mod 7)x (24 mod 7) mod 7? What do you notice about the last two quantities youcomputed?

Solution

Let's solve these one by one.

Step 1: Find 16mod716 \mod 7

To find 16mod716 \mod 7, we divide 16 by 7 and take the remainder.

16÷7=2remainder216 \div 7 = 2 \, \text{remainder} \, 2

So, 16mod7=216 \mod 7 = 2.

Step 2: Find 24mod724 \mod 7

Similarly, divide 24 by 7 and take the remainder.

24÷7=3remainder324 \div 7 = 3 \, \text{remainder} \, 3

So, 24mod7=324 \mod 7 = 3.

Step 3: Find 16×24mod716 \times 24 \mod 7

Now, multiply 16 and 24, and then find the result modulo 7.

16×24=38416 \times 24 = 384

Now, find 384mod7384 \mod 7.

384÷7=54remainder6384 \div 7 = 54 \, \text{remainder} \, 6

So, 16×24mod7=616 \times 24 \mod 7 = 6.

Step 4: Find (16mod7)×(24mod7)mod7(16 \mod 7) \times (24 \mod 7) \mod 7

From steps 1 and 2, we know that: 16mod7=2and24mod7=316 \mod 7 = 2 \quad \text{and} \quad 24 \mod 7 = 3

Now, multiply these values and find the result modulo 7.

2×3=62 \times 3 = 6

So, (16mod7)×(24mod7)mod7=6(16 \mod 7) \times (24 \mod 7) \mod 7 = 6.

Step 5: What do you notice?

The result of 16×24mod716 \times 24 \mod 7 and (16mod7)×(24mod7)mod7(16 \mod 7) \times (24 \mod 7) \mod 7 is the same. This illustrates a property of modular arithmetic:

(a×b)modm=[(amodm)×(bmodm)]modm(a \times b) \mod m = [(a \mod m) \times (b \mod m)] \mod m

This is known as the modular multiplication property.


Do you want details or have any questions?

Here are some related questions for practice:

  1. What is 25mod625 \mod 6?
  2. Calculate 30×18mod530 \times 18 \mod 5.
  3. What is 81mod981 \mod 9?
  4. Find 45×37mod845 \times 37 \mod 8.
  5. Calculate (25mod4)×(18mod4)mod4(25 \mod 4) \times (18 \mod 4) \mod 4.

Tip: Modular arithmetic is very useful in cryptography and number theory!

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Math Problem Analysis

Mathematical Concepts

Modular Arithmetic
Multiplication in Modular Systems

Formulas

a mod m = remainder when a is divided by m
(a × b) mod m = [(a mod m) × (b mod m)] mod m

Theorems

Modular Multiplication Property

Suitable Grade Level

Grades 9-12