







Formula when i know the GST total 
20171031 

From Duncan: HI  I've added up the GST from a pile of receipts and would like to know what the total cost of goods would be without GST. I don't want to add up 100's of receipts again with the cost before GST but I do need this total cost.
i.e.) I know I paid $400 GST, what would the formula be to find out the cost of what I purchased before taxes? Your help is much appreciated! Answered by Penny Nom. 





formula when i know the GST total 
20171031 

From Duncan: HI  I've added up the GST from a pile of receipts and would like to know what the total cost of goods would be without GST. I don't want to add up 100's of receipts again with the cost before GST but I do need this total cost.
i.e.) I know I paid $400 GST, what would the formula be to find out the cost of what I purchased before taxes? Your help is much appreciated! Answered by Penny Nom. 





Why does 10x10x10 give 1,000.0000000000001? 
20170412 

From Randolph: Hi, On your calculator I found that a box 10 by 10 by 10 inches has a volume of 1,000.0000000000001 cubic inches. Can you explain the numeral 1 thirteen places past the decimal? Thanks, Randy Answered by Penny Nom. 





2,0061234...484950 
20160924 

From Mimi: Compute the following:
2,0061234…484950 Answered by Penny Nom. 





600(1+0.05)^7 
20160421 

From chelsey: I am unsure on how to solve this problem, 600(1+0.05) 7 ? Answered by Penny Nom. 





I was paid 67% of the total owed 
20160125 

From Julie: I was paid $27000. This is 67% of the Total Owed. The Total Owed is unknown. How do I calculate the amount of the Total Owed? Answered by Penny Nom. 





777777 times 111111 
20100707 

From Chew: What is 777777 times 111111 without using a calculator? Answered by Chris Fisher. 





Figure out the square root of something 
20091220 

From eric: is there an ez equation to figure out the square root of something? Answered by Harley Weston. 





Acreage calculation 
20091029 

From Angela: I am appraising a small portion of property for a right of way for a new sewer line. I have appraised many similar
projects in the past; however the engineer always calculated the exact acreage and/or dimensions of the parcel
being taken. My survey states the following: "141 linear ft. of 25' permanent R/W. I divided the linear feet x 12 and mult. by 25
to get the square footage, but it just doesn't seem right. Any suggestions? Am I missing something? Answered by Robert Dawson. 





(570 divided by 15) multiplied by (5 plus 26) 
20090624 

From Sherrie: What is the answer to this math question:
(570 divided by 15) multiplied by (5 plus 26)..........
Thank you,
Sherrie:) Answered by Penny Nom. 





36cm to the second power divide 10cm 
20090226 

From val: 36cm to the second power divide 10cn Answered by Penny Nom. 





How accurate is the following calculation? 
20080903 

From Craig: Given that these numbers are only accurate to 2 decimal places, how accurate is the following calculation?
1.73  2.16 + 0.08 + 1.00  2.23  0.97 + 3.02 = 0.47
How do I work out the accuracy? Answered by Penny Nom. 





A one pass calculation of standard deviation 
20070319 

From Murtaza: Hi
I searched the listings but couldn't find what i am looking for. I have a dataset and i am allowed only 1 pass through it. At the end of this pass i must have the mean and standard deviation. Calculating the mean is easy as also demonstrated in your listings. I think the same can be done for standard deviation as well. But the doubt that i have is this : Will the calculated standard deviation be sequence dependent ? i.e. if i change the order in which the data items enter the system, will the std deviation also change ??
Thanks in advance
Murtaza Answered by Penny Nom. 





Calculations 
20021215 

From Mahdi: This problem is rather general, but it usually makes a lot of problems. I almost have no difficulty in math and physics questions, but unfortunately I'm not at all accurate in simple one or two digit calculation. I even sometimes make silly mistakes in simple sums like 7+4=12 or 4+5=11! Is there any effective way to reduce these mistakes? Answered by Walter Whiteley. 





A calculation with 6 numbers 
20010616 

From Edwin: I'm asked to come with, and program (in Ansi C) an algorithm that calculates all the possible results of a calculation with 6 numbers and one result. For example: I want all calculations with the numbers 3, 3, 8, 8, 2, 9, and with a result of 786. all numbers may be used once, arithmetical operations allowed are +  / *, fractions are not allowed. The problem here is what is a fast method to do this (i.e. what's algorithm that can to this). Answered by Claude Tardif. 





Human Calculator 
19980914 

From Pam Sloan: I recently saw a special on NBC Dateline about a man known as the human calculator. They called him Mr. Math. I want to know more about his books, seminars, and activities. Also, what is his real name? Answered by Patrick Maidorn. 

