Question

sr9897139 answer this ​

Answer 1

$\large\bf\underline\red{Answer \: :-}$

6) If a,b and c are in athematic progression then, b-a/c-b is equal to _____.

→ Answer is 1

___________________________________________

7) The 30th term of 10,7,4.... is

→

We have,

• First term = a = 10
• Difference = d = t2 - t1 = 7 - 10 = -3
• Number of term = n = 30

We use the formula

${\large{\underline{\boxed{\rm{\red{S_{n} = a +(n-1)d}}}}}}$

By using formula,

$\sf\longrightarrow{S_{30} = 10 + (30 - 1) - 3} \\ \\ \sf\longrightarrow{S_{30} = 10 + (29) - 3 } \: \: \: \: \: \: \: \\ \\ \sf\longrightarrow{S_{30} = 10 + ( - 87) \: \: \: \: \: \: \: \: \: \: \: } \\ \\ \sf\longrightarrow{S_{30} = - 77 } \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:$

30th term is -77.

Option [D] is correct answer.

_________________________________________

8) Find the sum of first 20 terms of the AP 3,3,3,....

→

We have,

• a = 3
• d = t2 - t1 = 3 - 3 = 0
• n = 20

We use formula

${\large{\underline{\boxed{\rm{\red{S_{n} = \frac{n}{2} [2a + (n-1)d] }}}}}}$

By using formula,

$\sf\longrightarrow{S_{20} = \frac{20}{2} [2(3) + (20 - 1)0]} \\ \\ \sf\longrightarrow{S_{20} =10 [6 + (19 )0]} \: \: \: \: \: \: \: \: \: \: \: \: \: \\ \\ \sf\longrightarrow{S_{20} = 10(6)} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \\ \\ \sf\longrightarrow{S_{20} = 60} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:$

Sum of the first 20 term is 60.

Option [B] is correct answer.

▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬