A series is formed by a n consecutive natural number or n consecutive even number or n consecutive odd number or n consecutive multiple. In which difference between to nearby numbers is always same. This difference is called **Common Difference. **

**Ex :- **

5, 6, 7, 8 . . . . 49, 50 Common difference **d **is 1.

4, 8, 12, 16 . . . . . . . . .76, 80 common difference **d **is 4.

You can find number of terms in a given series by following formula

sum of series can be find by given formula

for video explanation visit Youtube video

**Related questions for practice**

**1. **Sum of 120 + 135 + 150 . . . . . 600 is

**a. **11880** ** **b.** 11000 **c.** 23760 **d. **11800

**2. **2 + 4 + 6 + 8 . . . . . . . 60 is equal to

**a. **726 ** ** **b.** 1225 **c.** 930 **d. **11800

**3. **Sum of 15 term of series 1 + 3+ 5 + 7 + 9 . . . . . . . . is

**a. **250** ** **b.** 240 **c.** 265 **d. **225

**4.** Sum of first 20 consecutive odd number is

**a. **210 ** ** **b.** 300 **c.** 400 **d. **420

**5. **Sum of 7 consecutive even number is 140 then greatest even number is

**a. **26** ** **b.** 24 **c.** 22 **d. **28

**6.** Sum of seven consecutive odd number is 133 then lowest odd number is

**a. **17 ** ** **b.** 19 **c.** 11 **d. **13

**7. **Sum of 72 + 80 + 88 . . . . . .400 is

**a. **9912** ** **b.** 11912 **c.** 9112 **d. **8912

**8.** 130 + 125 + 120 . . . . . . + 40 is equal to

**a. **595** ** **b.** 630 **c.** 376 **d. **1190

**9.** 100 + 200 + 300 . . . . . . + 1000 is equal to

**a. **4500 ** ** **b.** 5500 **c.** 23760 **d. **11800

**10. **28 + 30 + 32 + 34 . . . . . . . . . . 80 is equal to

**a. **1188 ** ** **b.** 2458 **c.** 1258 **d. **1458

**Answer Key**

**1. **a **2. **c **3. **d **4. **c **5. **a

**6. **d **7. **a **8. **a **9. **b **10. **d