Why doesn't it add up correctly? 1

[Nottoobright]

I have an expenses form which usually adds up correctly, however when I put in the following figures it adds up with this reacurring number. Why?

The figures are:
4.50
2.95
6.80
7.70
2.40

and it adds them up to be:
24.349999999999998

instead of 24.35

The code is this:

var sub = 0;

if (T1.value > 0){
sub=sub + eval(T1.value)};
if (T2.value > 0){
sub=sub + eval(T2.value)};
if (T3.value > 0){
sub=sub + eval(T3.value)};
if (T4.value > 0){
sub=sub + eval(T4.value)};
if (T5.value > 0){
sub=sub + eval(T5.value)};
if (T6.value > 0){
sub=sub + eval(T6.value)};
if (T7.value > 0){
sub=sub + eval(T7.value)};
if (T8.value > 0){
sub=sub + eval(T8.value)};
if (T9.value > 0){
sub=sub + eval(T9.value)};
if (T10.value > 0){
sub=sub + eval(T10.value)};
if (T11.value > 0){
sub=sub + eval(T11.value)};
total.value= sub;

Thanks

 

[baad]

looks like this is the way math does it...
try something like:

var temp=24.349999999999998
temp=parseInt(temp*100)/100;
alert(temp) Victor

 

[Nottoobright]

Thanks Vituz that works great.

Thanks again.

 

[tsdragon]

The REASON that it happens is because computers don't use decimal, they use binary, and just as there are some fractions that don't come out even in decimal (e.g. 1/3) there are some that don't come out even in binary, so they become repeating. Unfortunately there are a LOT of numbers that do that. It's not easy to represent 10ths and 100ths in terms of 1/2's, 1/4's, 1/8's, 1/16's, etc. (that's binary's fractional parts). Any time you work with numbers with fractional parts via javascript you're likely to run into this problem, especially if you do anything more complex than addition and subtraction. Tracy Dryden
tracy@bydisn.com

http://www.bydisn.com

Meddle not in the affairs of dragons,
For you are crunchy, and good with mustard.

 

[baad]

gooood post, Tracy even i understood it Victor