# AnsweredCompressive strength of concrete cubes

#### VIDHYA SAGAR

##### Senior Member
While I am doing compressive strength of concrete cubes of size 150x150x150mm, one of my helper given other way of calculation.

For example load of failure comes 900 means, we can calculate 900/22.5= 40 N/mm2.

But he explains that, (900/45)*2 = 40 N/mm2.

Similarly for 1000 means, 1000/22.5= 44.44 N/mm2.
As per his explain (1000/45)*2 = 44.44 N.mm2.

While asking how he came to know this, he replied he is dividing the three sides (15+15+15 = 45) and multiplying by 2.

If any one knows, please explain.

Regards,
Vidhyasagar.

rameshchandrapatel

#### Dnyan Deshmukh

Staff member
Simple, he did some trick but math helped him

We divide it by 22.5

He is dividing by 45 and multiplying by 2

45/2 is 22.5

Example

1000 / 22.5 is our forumla

22.5 = 45/2

So

1000 / 45 / 2

Which cimes to

(1000 / 45 ) × 2

Its mathematics.

Now take example of 100 x 100 x 100 cube
It will some to 30
What will be his forumula

(1000 / 30) *2

Now he will go wrong

As the forumula for 100mm cube is divided by 10

His forumula will end up with 15.

May be he is lucky to discover this but will not apply on other cube sizes.

Thanks

#### MAR

##### Founder Member
Simple, he did some trick but math helped him

We divide it by 22.5

He is dividing by 45 and multiplying by 2

45/2 is 22.5

Example

1000 / 22.5 is our forumla

22.5 = 45/2

So

1000 / 45 / 2

Which cimes to

(1000 / 45 ) × 2

Its mathematics.

Now take example of 100 x 100 x 100 cube
It will some to 30
What will be his forumula

(1000 / 30) *2

Now he will go wrong

As the forumula for 100mm cube is divided by 10

His forumula will end up with 15.

May be he is lucky to discover this but will not apply on other cube sizes.
Well explained

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