Write a program that calculates sum of the integers numbers

What is the product if the question is write a program that calculates and prints the sum of the even integers from 2 to 30?

Answer 1

[Florin Neacsu]

2+4+6+...+30=2(1+2+3+...+15)=2*(15*16)/2=15*16

So 2+4+...+n = floor(n/2)*(floor(n/2)+1).

Regards, Florin

Answer 2

[Matt Fig]

The product would be the sum of the even integers from 2 to 30 ;-).

Seriously, what have you tried so far on this homework problem?

[Sean de Wolski]

You might need some bubble wrap for that.

[Paulo Silva]

I hate when it takes more time to understand what people want than to make their answer!

Answer 3

[Paulo Silva]

v=2:30;
sum(v(~mod(v,2)))

[Brother_Devil]

Hi Paulo, this works fine but what is operator ~ doing here? Its hard to understand what exactly is happening after ~. I am new to coding.

[Image Analyst]

mod(v, 2) will be either 0 or 1. The tilde inverts that, so 0 becomes 1, and 1 becomes 0.

[DGM]

Importantly, using ~ implicitly casts the numeric result from mod() to logical (along with doing the inversion). Otherwise, the indexing operation would fail if the indices were numeric 0 and 1, as you'd be trying to access the zeroth element of v.

Answer 4

[Doug Eastman]

or

sum(2:2:30)

[Paulo Silva]

that's simple but if you change the start value from 2 to 1 you do the sum of odd numbers instead, also if the last value is 31 or some odd number the result won't be correct, unfortunately that's not very flexible code.

[Paulo Silva]

btw that does work and is a good answer for the question (only if the values don't change), +1 vote

Answer 5

[Matt Tearle]

disp(240)

Or, for pedants who claim that evaluation is not the same as calculation,

disp(239+1)

[Sean de Wolski]

This is definitely the most compact and efficient way to do this. +1.