This method is to find square of the numbers which has unit’s digit as 5. i.e.: 25, 45, 65, etc.
You can find square of these numbers by three easy steps.
Step 1: Multiply ten’s digit with its next number.
Step 2: Find square of unit’s digit. i.e.: Square of 5.
Step 3: Write answers of step 1 and step 2 to together or side by side.
Let’s take examples.
Find square of 35
Step 1: Multiply ten’s digit with its next number.
3 × ( 3 + 1 ) = 3 × 4 = 12
Step 2: Find square of unit’s digit. i.e.: Square of 5.
Square of 5 = 25
Step 3: Write answers of step 1 and step 2 to together.
Answer = 1225
Find square of 65
Step 1: Multiply ten’s digit with its next number.
6 × ( 6 + 1 ) = 6 × 7 = 42
Step 2: Find square of unit’s digit. i.e.: Square of 5.
Square of 5 = 25
Step 3: Write answers of step 1 and step 2 to together.
Answer = 4225
Find square of 95
Step 1: Multiply ten’s digit with its next number.
9 × ( 9 + 1 ) = 9 × 10 = 90
Step 2: Find square of unit’s digit. i.e.: Square of 5.
Square of 5 = 25
Step 3: Write answers of step 1 and step 2 to together.
Answer = 9025
Find square of 115
Step 1: Multiply ten’s digit with its next number.
11 × ( 11 + 1 ) = 11 × 12 = 132
(Note: We are taking whole 11 as a ten’s digit.)
Step 2: Find square of unit’s digit. i.e.: Square of 5.
Square of 5 = 25
Step 3: Write answers of step 1 and step 2 to together.
Answer = 13225
Find square of 215
Step 1: Multiply ten’s digit with its next number.
21 × ( 21 + 1 ) = 21 × 22 = 462
(Note: We are taking whole 21 as a ten’s digit.)
Step 2: Find square of unit’s digit. i.e.: Square of 5.
Square of 5 = 25
Step 3: Write answers of step 1 and step 2 to together.
Answer = 46225
