Riddles and Brain Teasers

You Twirl My Body

You twirl my body but I keep my head up high.
When I go in I keep things tight.

What am I?

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A screw.

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Tagged with What am I?

Twice the Sum of Its Digits

What number is twice the sum of it’s digits?

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18.

1 + 8 = 9
2 × 9 = 18

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Stocking the Shelves

Alfred and Bill are clerks at the local grocery store. Alfred can stock a shelf in 20 minutes, but Bill is new and takes 30 minutes. How long would it take for them to stock a shelf together?

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Working together they can stock a shelf at a rate of 1/20 + 1/30 (or 5/60) per minute. They’ll finish in 12 minutes

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Debbie’s Dragster

Debbie starts driving her dragster from rest and constantly accelerates to 60 mph in 10 seconds. How far does she travel in those 10 seconds?

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1/12 mileTen seconds is 1/6 of a minute and 1 minute is 1/60 of an hour, so 10 seconds is 1/360 of an hour.If you graph her trip with the speed on the y-axis and the time on the x-axis, you get a triangle with height of 60 mph and width of 1/360 of an hour. To calculate the area of the triangle, you multiply 1/2 × 1/360 × 60 = 1/12.

1/12 mile

Ten seconds is 1/6 of a minute and 1 minute is 1/60 of an hour, so 10 seconds is 1/360 of an hour.

If you graph her trip with the speed on the y-axis and the time on the x-axis, you get a triangle with height of 60 mph and width of 1/360 of an hour. To calculate the area of the triangle, you multiply 1/2 × 1/360 × 60 = 1/12.

Posted in Brain Teasers

Ten White Man On A Dirt Road

Ten white men standing on a dirt road.
Killed by three eyes as black as night.

What happened?

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Someone bowled a strike. The ten white men are the pins, the dirt road is the bowling alley (it’s not dirt, but it’s the color of dirt, and if it said a smooth wooden alley it wouldn’t be much of a riddle). Three eyes as black as night are the finger holes in the bowling ball.

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Twenty from Three 3s

What’s the simplest way to make 20 using only three 3s (no other digits) and a combination of mathematical operations using any of these symbols?

+ – × / ^ ! √ . ()

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(3 + 3) / .3 = 20

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Counting Squares

How many squares of any size are in this grid?

4 x 4 grid

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30.There are:16 1×1 squares
9 2×2 squares
4 3×3 squares
1 4×4 square (the whole shape)Hence, 16 + 9 + 4 + 1 = 30.

30.

There are:

16 1×1 squares
9 2×2 squares
4 3×3 squares
1 4×4 square (the whole shape)

Hence, 16 + 9 + 4 + 1 = 30.

Posted in Brain Teasers

Has Wings But Cannot Fly

What has wings but can not fly.
Is enclosed, but can outside also lie.
Can open itself up or close itself away.
Is the place of kings and queens,
And doggerel of every means.
What is it upon which I stand,
Which can lead us to different lands?

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A stage.

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