For Rihan

 



Question 8

Given:
First term
Last term
Sum

(a) Formula to calculate sum of first terms


S_n = \frac{n}{2}(a + l)

(b) Find the total number of terms


220 = \frac{n}{2}(4 + 40)

220 = \frac{n}{2} \times 44 


220 = 22n

n = 10 

Answer: Number of terms = 10


(c) What should be added to the third term so that first three terms form a GP?

AP terms:
1st = 4
2nd = 8
3rd = 12

Let required number =

New third term =

For GP:


(8)^2 = 4(12 + x)

64 = 48 + 4x 


4x = 16

x = 4 

Answer: 4


Question 11

Given:
Length is 8 m more than breadth
Area = 384 sq.m

Let breadth = m
Length =

(a) Form the equation


x(x + 8) = 384

x^2 + 8x - 384 = 0 


(b) Find length and breadth


(x + 24)(x - 16) = 0

x = 16

Breadth = 16 m
Length = 24 m

Answer: Length = 24 m, Breadth = 16 m


(c) How much should length be decreased to make it a square?


24 - 16 = 8 \text{ m}

Answer: 8 m


Question 12

Given:
A circle with centre O
∠RMP and ∠RNP are angles standing on the same arc RP
∠ROP is the central angle


(a) Relation between ∠RMP and ∠RNP

Angles standing on the same arc are equal.


\angle RMP = \angle RNP

Answer: Equal


(b) Find ∠MRN

Given:


\angle MRN = (7x - 2)^\circ

\angle MPN = (3x + 10)^\circ 

Since they stand on the same arc:


7x - 2 = 3x + 10

4x = 12 


x = 3

\angle MRN = 7(3) - 2 = 19^\circ

Answer: 19°


(c) Relation between central and inscribed angle

Central angle is twice the inscribed angle.


\angle ROP = 2\angle RMP

Verified



Comments

Popular posts from this blog

Class 11 BS Chapter-6

Chapter-3 Planning (Business Studies)

Class 11-chapter 11