Question

Explain by giving step by step explanation of this question ​

Answer 1

Sorry brother , I was busy..

So , I said..the question will be solved by AP formula..

Circumference of circle= 2π r

therefore, circumference of semicirlce= πr

Circumference of circle with radius 1cm = π *1

Circumference of circle with radius 2 cm = π * 2

......

circumference of circle with radius 27 cm = π * 27

So the series is[ π *1 + π * 2... π *27]

taking pie common ..

π[1+2+3+4.....27]... equation 1

NOW , first term of AP is 1 and common difference is 1
SUM OF N TERMS IS GIVEN BY FORMULA ...
SN = N/2 *[2*a + (N -1)*d]

Sum of 27 terms .. = 27/2*[2*1+(27-1)*1]

= 27/2 *28

= 27*14

And putting sum of 27 terms in eq. 1... π(sum of 27 terms )

therefore , 22/7 * 27*14

= 22*2*27

Answer is 1188

Hope it helps you all❤❤❤

Answer 2

a=1 , d=1

sn= n

$sn = n \frac{1}{2} (2a + (n - 1)d \\ = 27 \frac{1}{2} (2 \times 1 + (27 - 1)1 \\ = 27 \frac{1}{2} (2 + 26) \\ = 27 \frac{1}{2} \times 28 \\ = 27 \times 14 \\ 278$