Let us make Ceasar Cipher table first. Here, we have to set to + 4 table. For that, we have to start letter e to set as A, f as B … likewise d as Z. Now, the + 4 Ceasar Cipher table looks like

The given plain text is
fvieo mr gshiw ger fi xvmgoc
To crack this secret code, follow the steps given below.
Step 1: Using Ceasar Cipher table, let us first match the most repeated letters. This will help us to progress faster.
fvieo mr gshiw ger fi xvmgoc

Step 2: Then, let us find remaining letters to complete the code.

Thus, the secret sentence is, BREAK IN CODES CAN BE TRICKY

The above figure clearly forms the sequence is 1, 1, 2, 3, 5, 8... Here, we find the pattern in which each number is in the Fibonacci sequence, obtained by adding together with previous two. Going on like this to find subsequent numbers at the twelfth month, we will get 144 pairs of rabbits. In the other words, twelfth Fibonacci number is 144.

STEP 1: Here, let p = 255, q = 204 and r = 68 Check whether p = q or p > q or p < q. Here p > q.
STEP 2: Let us find the HCF of 255 and 204 first. Now, subtract smaller number from larger number till p = q.

Now p = q, Hence, we conclude that the HCF of 255 and 204 is 51.
STEP 3: Now repeated same procedure for r – HCF (p, q) Now, subtract smaller number from larger number till HCF (p, q) = r.

Now HCF (p, q) = r, Hence, we conclude that the HCF of 255, 204 and 68 is 17. Comparing both the repeated division and repeated subtraction methods, in finding the HCF, we can conclude that the repeated subtraction, in one way is easier and gives the HCF faster that the repeated division and one would want to easely do subtraction rather than division. Isn’t it?

STEP 1: Here , take m = 144 and n = 120 Check whether m = n or m > n or m < n. Here m > n.
STEP 2: Subtract the smaller number from the larger number till m = n.

Now m = n , Hence, we conclude that the HCF of 144 and 120 is 24.

Take m = 196 mm and n = 168 mm,
Here m > n.
196 - 168 = 28
168 - 28 =  140
140 - 28 = 112
112 - 28 = 84
84 - 28 =  56
56 - 28 = 28
28 - 28 = 0
The length of the side of the biggest square is 28 mm.