Code Cracking

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Mathematics, Algebra and Function

Grade 5- 8

Objective

Students use codes to learn pre-algebra concepts.

Directions

Facts and Reminders
Simple Codes
This is a simple code because 43 + 32 = 75.
43
+ 32 A = 7 C = 5
AC

Using Reverse Operations
In the problem below, to crack the code you must subtract 98 from 123. The answer is 25.
Problem Step Check Solution
98 98
+ DF 123 - 98 = 25 + 25 D = 2 F = 5
123 123

In this next problem, to crack the code, you must divide 1,428 by 42. The answer is 34.
Problem Step Check Solution
42 42
x AF x 34
168 1428 ÷ 42 = 34 168 A = 3 F = 4
1260 1260
1428 1428

Using Number Sense
In the problem below, you can try two ways to crack the code. One way is to try each digit 1 through 9. Another way is knowing that 6 = 2 x 3 and trying 2 first.
Problem Check Solution
31 31
x AA x 22
6A 62 A = 2
6A0 620
68A 682

In the next problem, you know that the only number that added to itself and equals 2 is 1.
Problem Check Solution
BBB 111
+ BBB + 111 B = 1
2 2 2 222

In the problem below, ask yourself the question, "Which number times itself equals 9?" The answer is 3.
Problem Check Solution
FFF 333
x F x 3 F = 3
999 999

Resources

  • Code Cracking activity sheet
  • pencils

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