2191 . If the radius of a circle is decreased by 20% then the area is decreased by:

A. 20%
B. 30%
C. 36%
D. 40%

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Answer: Option C

Explanation:

When the radius of a circle is decreased by 20%, the new radius becomes 80% (100% - 20%) of the original radius.

Let's denote the original radius as "R" and the new radius as "0.8R" (80% of R).

Now, let's calculate the areas of the original circle and the new circle:

The area of the original circle with radius R is πR^2.
The area of the new circle with radius 0.8R is π(0.8R)^2.

To find the percentage decrease in the area, we can compare the areas of the new and original circles:

(π(0.8R)^2 - πR^2) / (πR^2) * 100%

Simplify:

[(0.8R)^2 - R^2] / R^2 * 100%

Now, calculate:

[(0.64R^2 - R^2) / R^2] * 100%

Simplify further:

[(-0.36R^2) / R^2] * 100%

The R^2 terms cancel out:

-0.36 * 100%

So, the area is decreased by 36%. Therefore, the correct answer is 36%.

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সোনালী ও জনতা ব্যাংক - অফিসার(আইটি) - 02.10.2021

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2192 . If the radius of a circle is increased by 1% then the area of that circle increases by what percent?

A. 1.01%
B. 1.1%
C. 2.1%
D. 2.01%
E. None of these

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Answer: Option D

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2193 . If the radius of a circle is increased by 100%, by what % is the area of the circle increased?

A. 100%
B. 200%
C. 300%
D. 400%

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Answer: Option C

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সমন্বিত ৭ ব্যাংক || অফিসার (ক্যাশ) (24-05-2024)

A. 44%
B. 400%
C. 40%
D. 120%

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Answer: Option A

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যুব ও ক্রীড়া মন্ত্রণালয়ের যুব উন্নয়ন অধিদপ্তর | ক্যাশিয়ার | ০৪.০৫.২০১৮

A. .36%
B. 3.6%
C. 6%
D. 12.36%
E. 36%

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Answer: Option D

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2196 . If the radius of a circle is reduced by 40%, its circumference is reduced by-

A. 60%
B. 40%
C. 35%
D. 30%

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Answer: Option B

Explanation:

If the radius of a circle will be reduced by 40% its circumference will also be reduced by 40% because circumference of circle is directly dependent on radius of the circle as the formula to find the circumference is Circumference= 2πr or πd
d is diameter which is 2r

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Janata Bank PLC || Officer (Rural Credit) (27-10-2023) || 2023

A. multiplied by 3
B. multiplied by 6
C. multiplied by 9
D. multiplied by 12

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Answer: Option A

Explanation:

When the radius of a circle is tripled, the circumference is multiplied by 3.

The formula for the circumference of a circle is C = 2πr, where "C" is the circumference and "r" is the radius. If you triple the radius, the new radius becomes 3r.

So, the new circumference will be:

New Circumference = 2π(3r) = 6πr

This is three times the original circumference (2πr), which means it's multiplied by 3.

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সহকারী পরিচালক(AD) -12.11.2021

A. Tk 4630.00
B. Tk 4630.50
C. Tk 4631.50
D. Tk. 4632.00

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Answer: Option B

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সমন্বিত ৭ ব্যাংক ও ১টি আর্থিক | সিনিয়র_অফিসার | 27-11-2021

A. 3%
B. 12%
C. 10%
D. 8%

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Answer: Option B

Explanation:

The ratio of the principal amount (P) to the yearly amount (A) is given as 25:28. This means:

P/A = 25/28

To find the yearly rate of interest (R), we can use the formula for simple interest:

Simple Interest (SI) = (P * R * T) / 100

Where: SI = Simple Interest P = Principal amount R = Rate of interest (yearly rate) T = Time (in years)

We are given that the ratio of P to A is 25:28, which means:

P/A = 25/28

So, we can express P in terms of A as:

P = (25/28) * A

Now, let's calculate the simple interest using the given principal and yearly amount:

SI = A - P

Substitute the values of P and A:

SI = A - [(25/28) * A]

To find the rate of interest (R), we need to find the percentage of SI with respect to the principal amount (P):

R = (SI / P) * 100

R = { [A - (25/28) * A] / [(25/28) * A] } * 100

Simplify the expression:

R = { [28A - 25A] / (25A) } * 100

R = (3A / 25A) * 100

R = (3/25) * 100

R = 12%

So, the yearly rate of interest is 12%.

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সমন্বিত ৭ ব্যাংক || সিনিয়র অফিসার-05-11-2021 ||

A. 12 years
B. 8 years
C. 10 years
D. 16 years

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Answer: Option B

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জনতা ও রূপালী ব্যাংক- অফিসার ১৩.১২.২০১৯

A. 15 : 5 : 3
B. 15 : 5 : 7
C. 3 : 15 : 5
D. 15 : 3 : 5

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Answer: Option A

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জনতা ও রূপালী ব্যাংক- অফিসার ১৩.১২.২০১৯

A. 3/5
B. 2/7
C. 1/3
D. 1/2

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Answer: Option A

Explanation:

আমরা জানি,
বৃত্তকলার ক্ষেত্রফল = θ/360πr2

বৃত্তের ক্ষেত্রফল = πr2

শর্তমতে, θ/360πr2:πr2=3:5

⇒θ360πr2/πr2 =3/5

⇒θ/360=3/5

.:. বৃত্তকলার দৈর্ঘ্য ও বৃত্তের পরিধির অনুপাত = θ/360×2πr
____________
2πr

=θ/360=3/5

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জীবণ বীমা কর্পোরেশন (সহকারী ম্যানেজার) 16-10-2020

2203 . If the ratio of the areas of 2 squares is 2:1, then the ratio of the perimeters of the squares is

A. $1 : 2$
B. $1 : \sqrt{2}$
C. $2 : 1$
D. $\sqrt{2} : 1$

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Answer: Option D

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Bangladesh Bank - Assistant Director - 2010

A. 4 : 9
B. 9 : 4
C. 2 : 3
D. 3 : 4

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Answer: Option B

Explanation:

area of circle = pi * r2
a1 / a2 = r1 2 / r2 2 = (3) 2 / (2) 2 = 9 / 4

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2205 . If the ratio of two numbers is 3: 4 and their least common multiple is 60, then the numbers are-

A. 15, 20
B. 12, 16
C. 9,12
D. 18, 24

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Answer: Option A

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সমন্বিত ৮টি ব্যাংক ও ১টি আর্থিক প্রতিষ্ঠান - সিনিয়র অফিসার (16-05-2025)

2191 . If the radius of a circle is decreased by 20% then the area is decreased by:

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2192 . If the radius of a circle is increased by 1% then the area of that circle increases by what percent?

2193 . If the radius of a circle is increased by 100%, by what % is the area of the circle increased?

2194 . If the radius of a circle is increased by 20% then the area is increased by :

2195 . If the radius of a circle is increased by 6%, then the area of the circle is increased by ---

2196 . If the radius of a circle is reduced by 40%, its circumference is reduced by-

2197 . If the radius of a circle is tripled, the circumference is

2198 . If the rate if interest is 10 % per annum and is comunded half yearly , the principal of Tk.l 4000 in years will amount to-

2199 . If the ratio of principal and yearly amount be in the ratio 25: 28, then the yearly rate of interest is

2200 . If the ratio of simple interest and principal is 8 : 25 and rate of interest is equal to the time invested then find the time of investment ?

2201 . If the ratio of speed of doing work of the persons is 1 : 3 : 5 , what is the ratio of this taken by these people to do the same amount of work ?

2202 . If the ratio of the area of a sector to the area of the circle is 3:5. What is the ratio of the legth of theare in the sector to the circumference of the circle?

2204 . If the ratio of the radii of the two circles is 3 : 2, than the ratio of the areas of the two circles is:

2205 . If the ratio of two numbers is 3: 4 and their least common multiple is 60, then the numbers are-

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