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2 years ago

The sum of the areas of two circles is 80n square meters. Find the length of a radius of each circle if

Mathematics

1 answer:

astra-53 [7]2 years ago

4 0

Answer:

8 meters.

Step-by-step explanation:

Let the 2 radii be x and 2x, then
π x^2 + π (2x)^2 = 80π

π x^2 + π 4x^2= 80π

x^2 + 4x^2= 80

5x^2 = 80

x^2 = 16

x = 4.

So the radius of the larger circle = 2*4 = 8 m.

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tensa zangetsu [6.8K]

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Brilliant_brown [7]

Answer:

-5

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2 - 1 = 1

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2 years ago

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2 years ago

Given the sequence 1/2 ; 4 ; 1/4 ; 7 ; 1/8 ; 10;.. calculate the sum of 50 terms

miv72 [106K]

Hint :-

Break the given sequence into two parts .
Notice the terms at gap of one term beginning from the first term .They are like $\dfrac{1}{2},\dfrac{1}{4},\dfrac{1}{8}$ . Next term is obtained by multiplying half to the previous term .
Notice the terms beginning from 2nd term , $4,7,10,13$ . Next term is obtained by adding 3 to the previous term .

Solution :- 

We need to find out the sum of 50 terms of the given sequence . After splitting the given sequence ,

$\implies S_1 = \dfrac{1}{2},\dfrac{1}{4},\dfrac{1}{8}$ .

We can see that this is in Geometric Progression where 1/2 is the common ratio . Calculating the sum of 25 terms , we have ,

$\implies S_1 = a\dfrac{1-r^n}{1-r} \\\\\implies S_1 = \dfrac{1}{2}\left[ \dfrac{1-\bigg(\dfrac{1}{2}\bigg)^{25}}{1-\dfrac{1}{2}}\right]$

Notice the term $\dfrac{1}{2^{25}}$ will be too small , so we can neglect it and take its approximation as 0 .

$\implies S_1\approx \cancel{ \dfrac{1}{2} } \left[ \dfrac{1-0}{\cancel{\dfrac{1}{2} }}\right]$

$\\\implies \boxed{ S_1 \approx 1 }$

$\rule{200}2$

Now the second sequence is in Arithmetic Progression , with common difference = 3 .

$\implies S_2=\dfrac{n}{2}[2a + (n-1)d]$

Substitute ,

$\implies S_2=\dfrac{25}{2}[2(4) + (25-1)3] =\boxed{ 908}$

Hence sum = 908 + 1 = 909

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2 years ago

7 tens x 10 in standard form

rosijanka [135]

Answer:

700

Step-by-step explanation:

7 tens is 70. 70*10=700.

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2 years ago