Question

There are 20 students in each class. One candy was given to the first student and four to the second. Each student got three candies more than his predecessor. How many candies in all were needed for 20 students?

Answer 1

58 candies were required

Answer 2

Answer:

Step-by-step explanation:

First student = 1 candy

2nd student = 4 candies

3rd student = 7 candies  and so on  ( 20 students)

so, by using Arithemtic Progression we can solve this sum

1 + 4 + 7 + -------------------------------------- upto 20 students

first term    = a = 1

common difference  = d = 4-1 = 3

n  = 20

so,

S20 = n/2 ( 2a + (n - 1) d)

       = 20 / 2 ( 2 (1) + ( 20 - 1) 3 )

       =  10 ( 2 + 19 x 3)

       =  10 ( 2 + 57)

       = 10 x 59

       = 590

590 candies needed for 20 students