# Coincidental numbers

#### neonstrobe

Joined May 15, 2009
189
Just checking an algorithm I stumbled on a slightly interesting result. The expression is
5/(1.5**4).
Needs answer to 9 decimal points.

#### dl324

Joined Mar 30, 2015
16,118
What makes it interesting? There's no way to get the wrong answer because they included parenthesis to force an order of operations that's already understood.

#### wayneh

Joined Sep 9, 2010
17,469
My old favorite from back in the heyday of the hand calculator is 987654321 ÷ 123456789.

#### Wendy

Joined Mar 24, 2008
23,319
Just checking an algorithm I stumbled on a slightly interesting result. The expression is
5/(1.5**4).
Needs answer to 9 decimal points.
What is the double **?
$$\frac{5}{1.5•4}$$?

Last edited:

#### neonstrobe

Joined May 15, 2009
189
Sorry. I'll rephrase that in Basic: 5/1.5^4 (without redundant parentheses).
Just means raise to the power. It's the Fortran version.

#### jpanhalt

Joined Jan 18, 2008
11,087
Thanks.
That changes the interesting level a little.

0.987654321

#### Wendy

Joined Mar 24, 2008
23,319
$$x=\frac{5}{1.5^4}$$

Practicing my LaTex skills.

The M$calculator can handle more than 8 digits. I get 0.98765432098765432098765432098765 Last edited: #### crutschow Joined Mar 14, 2008 33,339 My old favorite from back in the heyday of the hand calculator is 987654321 ÷ 123456789. And you only need one decimal place for the answer. #### Wendy Joined Mar 24, 2008 23,319 $$\frac{987654321}{123456789}=8.000000072900000663390006036849$$ Trolling Moderator style. Last edited: #### crutschow Joined Mar 14, 2008 33,339 $$\frac{987654321}{123456789}=8.000000072900000663390006036849$$ OK, you only need 1 decimal place for a engineering answer. #### wayneh Joined Sep 9, 2010 17,469 $$\frac{987654321}{123456789}=8.000000072900000663390006036849$$ Trolling Moderator style. Just curious. What did you use to get that many digits? Excel drops anything past 729. Another calculator I have gives ...72900001 using double precision and ...72900000664 using float80. Last edited: Thread Starter #### neonstrobe Joined May 15, 2009 189 $$x=\frac{5}{1.5^4}$$ Practicing my LaTex skills. View attachment 227764 The M$ calculator can handle more than 8 digits.

I get 0.98765432098765432098765432098765
Yes, that's why I said to 9 decimal digits of precision. The repeat count gets approximated.
Could not have been exact with a factor of 3 in the denominator, really!
My old calculator displays 9 digits but has an accuracy to about 12. You have to subtract some MSD's to see the remainder. Which is how I came across this.

#### Wendy

Joined Mar 24, 2008
23,319
Just curious. What did you use to get that many digits? Excel drops anything past 729. Another calculator I have gives ...72900001 using double precision and ...72900000664 using float80.