CAT 2008: Quantitative Questions a Day 1 to 50 - The discussions

[rajeev_hts]

It was a sitter.

Answer is (2) 40/3.

To get the point of contact 10 other circle will be of radius >10.

In Tr(O2 O1 p)

(r- 8 ) / (r+ 8 ) = 2/8

r=40/3

[slam]

here's the diagram, for your reference. hope it helps.


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slam.

[ankaj]

Originally Posted by srikar2097

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Quantitative Question # 018
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Two spherical balls lie on the ground touching. If one of the balls has a radius of 8 cm, and the point of contact is 10 cm above the ground, what is the radius of the other ball?
(1) 18 cm (2) 40/3 cm (3) 25/2 cm (4) 13 cm (5) none of the these
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Answer: 40/3

[sabsebadapaagal]

Originally Posted by srikar2097

------------------------------------------------------
Quantitative Question # 018
------------------------------------------------------
Two spherical balls lie on the ground touching. If one of the balls has a radius of 8 cm, and the point of contact is 10 cm above the ground, what is the radius of the other ball?
(1) 18 cm (2) 40/3 cm (3) 25/2 cm (4) 13 cm (5) none of the these
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Answer is 40/3 i.e option 2

The triangles in two circles will be similar

Let R be the radius to be found

thus R/4 + 10 =R {I have skipped a few steps... }

=> R=40/3

[schinnar]

------------------------------------------------------ Quantitative Question # 018 ------------------------------------------------------ Two spherical balls lie on the ground touching. If one of the balls has a radius of 8 cm, and the point of contact is 10 cm above the ground, what is the radius of the other ball? (1) 18 cm (2) 40/3 cm (3) 25/2 cm (4) 13 cm (5) none of the these Ans: Two sphers is touching each other lets consider it as S1 and S2 Radius of S1 is 8 cm. Let the point of contact be p. Here there is a transverse common tangent of the length 20cm through the point of contact Length of the transverse common tangent = sqrt((Distance betwen centre)^2 - (r1+r2)^2)(r1 - radius of the S2 r2 radius of the S1) Distancebetween ceter = r1+r2(imagine two circles touching each other) 20^2 = (r1+^2 - (r1 + ^2 400 = 32r1 =>r1=25/2 cm

[schinnar]

Ans: Two sphers is touching each other lets consider it as S1 and S2 Radius of S1 is 8 cm. Let the point of contact be p. Here there is a transverse common tangent of the length 20cm through the point of contact Length of the transverse common tangent = sqrt((Distance betwen centre)^2 - (r1+r2)^2)(r1 - radius of the S2 r2 radius of the S1) Distancebetween ceter = r1+r2(imagine two circles touching each other) 20^2 = (r1+^2 - (r1 + ^2 400 = 32r1 =>r1=25/2 cm Ans (3)

[getneonow]

weekend special..an easy QQAD

after drawing the proper figure we find that we r left with a right triangle whose hyp is 8+R and whose height is R-8 where R is the reqd radius of big circle.

but a perpendicular from point of contact to base is of length 10-8 = 2 cm

so similar right triangles with hyp and height resp as (8,2) and (8+R,R-

ratio of them is equal

=> 2/8 = R-8 / R+8

=> R = 40/3

PS: cudnt attach the figure.

Neo

[m2shines]

Ans is 40/3

applying similar triangles ->

(r-8 )/(r+8 ) = 2/8
so r = 40/3

just one doubt that can we assume sphere to be a circle here.
If we assume that from touching point we can draw 2 circles corresponding to 2 spheres, then is it dat we will be having radius as max thats 8 cm or we can have pt of contact being nt at the centre of sphere.

[shankey_595]

d ans is 40/3 application of similar triangles ....
and we can take these two spehers as two circles dont consider as a 3d figure suppose two spehers lying ina xy plane hope ur doubt is clear

[Aarav]

It's the start of mock season for most of you and I thought I should share my experience (personal as well what I have seen on people here in last 4 years) that might help you approach mocks better.

Rules

(1) Don't take the initial mock scores (either high or low) too seriously. The focus in the initial mocks should be on experimentation under extreme conditions (things like dropping your pencil off 5 minutes before the finish time etcetera).

(2) Spend at least 2 days with each paper to understand why you performed well or why or performed badly. And what are the learnings from this paper -> what mistakes you wouldn't ever repeat again.

(3) Finish the entire paper after the mock i.e. solve DI case lets, unsolved quant problems and RCs that you might have missed in the exam.

(4) Majority of those taking CAT aren't good in quant and they give more time to DI and VA/RC section. This in turn pushes the DI and VA/RC percentiles on lower side with same marks. Hence, those who are good at quant shouldn't neglect DI and treat this section as important as VA/RC if not more.

(5) The people who aren't that skillful in VA/RC must make it a habit to attempt all RCs in the exam. This is absolutely necessary to clear VA/RC cut-off in CAT. Read, political, science, philosophical, history journals from the net and read these slow to get subject familiarity.

(6) Each section (Quant/DI/Verbal) should be attempted in 50+/-5 minutes only.

(7) Quant -> we can discuss anytime on this thread Just one point to start with -> attempt with 100% accuracy even if that means you are attempting a little lesser. Speed can be increased later when more topics come under your grasp. Avoid guesses unless and until the probability of getting the right answer is 50%.