Read the numbers and decide what the next number should be. 5, 15, 6, 18, 7, 21, 8,…?

Solution:

It is given that,

numbers are in the series 5, 15, 6, 18, 7, 21, 8,… .

Here,

a₁ = 5, b₁ = 15,

a₂ = 3, b₂ = 18,

a₃ = 7, b₃ = 21,

a₄ = 8,

We know that,

b₁/a₁ = 15/5

b₁/a₁ = 3

b₁ = 3a₁

Then,

b₂/a₂ = 18/6

b₂/a₂ = 3

b₂ = 3a₂

and,

b₃/a₃ = 21/7

b₃/a₃ = 3

b₃ = 3a₃

Finally, a₄ = 8

So, the next term should be,

b₄ = 3a₄

b₄ = 3 × 8

b₄ = 24

Therefore, the next number should be 24.

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Read the numbers and decide what the next number should be. 5, 15, 6, 18, 7, 21, 8,…?

Summary:

The next number in 5, 15, 6, 18, 7, 21, 8,… should be 24.