Here's a schoolboy question:

I drill a hole 100mm long through the middle of a metal sphere. What's the volume of metal that's left in millilitres? You don't need any advanced maths like calculus, just ordinary arithmetic.

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I should be dead; I've cheated the Grim Reaper yet again by surviving my third heart attack in June.

I told you I was no good at homework.

If the teacher had said I had 3mm left over I would of started arguing,

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DIY | Donnas dream house

what diameter off hole!!!!
is the hole representing a 100mm sphere or somethung bigger but not full penetration

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we are all ------------------still learning

You have all the information you need.

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I should be dead; I've cheated the Grim Reaper yet again by surviving my third heart attack in June.

is the hole representing a 100mm sphere or somethung bigger but not full penetration

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we are all ------------------still learning

you can only drill a hole off sub 1mm in diameter otherwise it cant be 100mm

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we are all ------------------still learning

The hole goes THROUGH the sphere, all the way through & out the other side.

Hint:

The diameter of the sphere isn't specified, so it can be any provided it's big enough for a 100 mm long hole.

The diameter of the hole isn't specified, so it can be any provided the hole is 100 mm long.

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I should be dead; I've cheated the Grim Reaper yet again by surviving my third heart attack in June.

the trouble is if you drill a say a 50mm hole in a sphere the plug or cutout bit will havethe full sphere size in its centre say its a 150mm sphere the hole is going to be about 145 ish so not the same size !!!

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we are all ------------------still learning

9000mm3

9000 mm³ ? Sorry, no.

If the hole is to be 100mm long, The diameter must increase as the diameter of the sphere increases. For a set hole length, the volume that's left must be constant, no matter what the diameter of the sphere is. If it were not, you'd need calculus to work it out.

So if the diameter of the hole is made smaller, the diameter of the sphere gets smaller too. When the diameter of the hole is zero, the diameter of the sphere becomes 100mm. So the volume that's left is the volume of a 10cm dia sphere, i.e. 4/3 x Π x 5³ = 524 ml. (or 524,000 mm³) to the nearest ml.

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I should be dead; I've cheated the Grim Reaper yet again by surviving my third heart attack in June.

You could of put anything you liked there, and no body would of argued

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DIY | Donnas dream house

Pictures help:
http://www.ultimatehandyman.co.uk/attachment.htm

Can we just have another plank of wood to play with?
No drilling, just sawing.

dave

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You can always tell a Yorkshireman,
But you cannot tell him much.

Heres another one, bit easier though

Assume you have a huge length of string and wrap it all the round the earth at the equator.

How much longer would the string have to be to do the same exercise but this time its always 3 feet above the ground?

Again simple maths is all you need! You will be surprised by the answer

PS for the anal ones amoung us, lets forget that the earth is not a sphere and ignore mountains/ terains etc

Circumference = pi x diameter, so increasing the diameter of the circle the rope makes by 6ft makes very little difference compared to using the diameter of the earth on its own

Using calculator and a pencil and pad.

Circumference at the Equator =24,901.55 miles

Diameter = Circumference ÷ pi (22/7 or 3.142) = 7,923.2202 miles
= 13,944,867 yards.

Add 2 yards to raise rope 3 feet off the floor
= 13,944,869 yards.
= 7.923.221 miles

Circumference = Diameter x pi (22/7 or 3.142) = 24,901.551.

Difference is 0.001 miles = 1.76 yards

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You can always tell a Yorkshireman,
But you cannot tell him much.