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Help Strange problem with scientific calculator.

by sunny79
Tags: calculator, helpstrange, scientific
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sunny79
#1
Mar2-14, 10:27 AM
P: 36
I was doing chemical equilibrium problems where one of the steps required me to square the reciprocal.

Which was (1/4.2x10^52)^2

The correct answer for this is 5.7 x 10^-106 but my Casio FX 115 ES calculator keeps showing zero.

Can anyone please shed some insight on this. It would be greatly appreciated. I have used this calculator in the past with success. I never encountered such a problem before. I have my exam on Tuesday. BTW no graphing calculators are allowed. If this doesnot workout then I will have to purchase another scientific calculator.
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adjacent
#2
Mar2-14, 10:40 AM
PF Gold
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P: 1,488
Quote Quote by sunny79 View Post
Which was (1/4.2x10^52)^2

The correct answer for this is 5.7 x 10^-106
Welcome to PF
The calculator can't show a value greater than 99 or less than -99 in the power.(The maximum value available is 9*10^99 and minimum is (9*10^(-99))
(I have a Casio fx-100MS)
Borek
#3
Mar2-14, 10:59 AM
Admin
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P: 23,533
It is called an "arithmetic underflow".

Note that

[tex]\left(\frac 1 {4.2 \times 10^{52}}\right)^2 = \left(\frac 1 {4.2}\right)^2 \left(\frac 1 {10^{52}}\right)^2 = 0.057 \times \frac 1 {10^{104}} = 0.057 \times 10^{-104}[/tex]

10-104 part can be done in memory faster than it takes to key numbers into calculator - you just need to understand what is going on and how to deal with such a situation.

sunny79
#4
Mar2-14, 11:19 AM
P: 36
Help Strange problem with scientific calculator.

Thanks guys, that helped a lot. :)


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