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