If the first term of AP is 4 and the sum of first five term is equal to one-fourth of the sum of the next five term, then find the 15th term?

15th term = 116

Step-by-step explanation:

a= 4

Sum of an A.P = n/2 {2a + (n-1)d}

sum of first five term is equal to one-fourth of the sum of the next five term

5/2{ 2*4 + (5-1)d} = 1/4 × 10/2{2*4 + (10-1)d

5/2 {8 + 4d} = 1/4 × 5{ 8 + 9d}

40/2 + 20/2d = 1/4{ 40 + 45d)

20 + 10d= 40/4 + 45/4d

20 + 10d = 10 + 45/4d

20 - 10 = 45/4d - 10d

10 =45d - 40d /4

10 = 5/4d

Divide both sides by 5/4

10 ÷5/4 = d

10×4/5 = d

40/5 = d

8 = d

d= 8

Find the 15th term

15th term = a + (n-1)d

= 4 + (15-1)8

= 4 + (14)8

= 4 + 112

= 116

The 15th term is 116

plants store their excess carbohydrate in the form of starch so that it could be used as energy source later on. the excess carbohydrate is converted into starch in the plastid i.e. chloroplast & this process occurs in the presence of sunlight. it is an insoluble polymer of glucose which gets stored in cell organelles named as amyloplasts. in some plants, starch is also stored in roots and embryos.