Calculator giving weird answer when dividing factorial

Question

I am using a TI-34 MultiView

I was trying to divide the following

    20!/(17!3!)

The answer should be 1140 right?

the numerator is 2.43*10^18

the denominator is 2.12 * 10^15

when I divide the two I get I keep getting 1.14 * 10^33

For some reason the calculator is adding the exponents instead of subtracting when i divide?? can someone help me please i'm little confused

Answer 1

Order of operations is important. You probably typed:

2.43 * 10^18 / 2.12 * 10^15

which looks like:

$$ \frac{2.43 \times 10^{18}}{2.12} \times 10^{15} = \frac{2.43}{2.12} \times 10^{18 + 15} = 1.14 \times 10^{33} $$

what you meant was:

$$ \frac{2.43 \times 10^{18}}{2.12 \times 10^{15}} = \frac{2.43}{2.12} \times 10^{18 - 15} = 1.14 \times 10^3 = 1140 $$

so on your calculator you should have typed:

(2.43 * 10^18) / (2.12 * 10^15)