1. Adding a Sequence of numbers (Pairing Method)
1. Find the sum of ……
Problem Solving Strategy :-
Step 1 – Divide the last number by 2
50 ÷ 2 = 25{ to get the numbers of pairs }
Step 2 – Add 1 to the last number ( 50 )
= 51 { The sum of each pair is 51 }
Step 3 – Multiply the results from steps 1 and 2 :
25 x 51 = 1275

2. Adding a Sequence of numbers (Pairing Method)
Now you try : -
2. Find the sum of ……
What if the sequence of numbers that does not end with even numbers?
Now you try : -
3. Find the sum of ……
Now you try : -
4. Find the sum of ……

3. Adding a Sequence of numbers (Triangle Method)
1. Find the sum of ……
Problem Solving Strategy :-
Step 1 – Multiply the last number (50) by the next higher number (51) and divide the product by 2.
50 x 51 ÷ 2 = 1275
Now you try : -
2. Find the sum of ……

4. Adding a Sequence of numbers (Average Method)
What if the sequence of consecutive number does not start with 1?
1. Find the sum of ……
Problem Solving Strategy :-
Step 1 – Subtract the first number from the last number and add 1
(50 – 11) + 1 = 40{ to get the numbers of Terms }
Step 2 – Add the first number to the last number and divide the result by 2.
( ) ÷ 2 = 30.5 { The average is 30.5 }
Step 3 – Multiply the results from steps 1 and 2 :
40 x 30.5 = 1220
Now you try : -
2. Find the sum of ……

5. Adding a Sequence of numbers (Average Method)
Now you try : -
3. Find the sum of ……
Now you try : -
4. Find the sum of ……

6. Adding a Sequence of odd numbers
1. Find the sum of ……
Problem Solving Strategy :-
Step 1 – Add 1 to the last number and divide the last number by 2
(1 + 51)÷ 2 = 26{ to get both the Average and the numbers of Terms }
Step 2 – Square the results from step 1.
26 x 26 = 676
Now you try : -
2. Find the sum of ……

7. Adding a Sequence of odd numbers
What if the sequence of consecutive number does not start with 1?
1. Find the sum of ……
Problem Solving Strategy :-
Step 1 – Subtract the first number from the last number, divide it by 2 and add 1
(33 – 7) ÷ = 14{ to get the numbers of Terms }
Step 2 – Add the first number to the last number and divide the result by 2.
(7 +33) ÷ 2 = 20 { The average is 20 }
Step 3 – Multiply the results from steps 1 and 2 :
14 x 20 = 280
Now you try : -
2. Find the sum of ……

8. Adding a Sequence of even numbers
1. Find the sum of ……
Problem Solving Strategy :-
Step 1 – Divide the last number by 2
50 ÷ 2 = 25{ to get the numbers of Terms }
Step 2 – Add 2 to the last number and divide the sum by 2.
(50 + 2) ÷ 2 = 26 {to get the average}
Step 3 – Multiply the results from steps 1 and 2
25 x 26 = 650
Now you try : -
2. Find the sum of ……

9. Adding a Sequence of even numbers
What if the sequence of consecutive number does not start with 2?
1. Find the sum of ……
Problem Solving Strategy :-
Step 1 – Subtract the first number from the last number, divide it by 2 and add 1
(34 – 8) ÷ = 14{ to get the numbers of Terms }
Step 2 – Add the first number to the last number and divide the result by 2.
(8 +34) ÷ 2 = 21 { The average is 20 }
Step 3 – Multiply the results from steps 1 and 2 :
14 x 21 = 294
Now you try : -
2. Find the sum of ……