If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Lesson 3: Adding & subtracting rational numbers

# Adding & subtracting rational numbers: 0.79 - 4/3 - 1/2 + 150%

Sal evaluates 0.79 - 4/3 - 1/2 + 150%. Created by Sal Khan.

## Want to join the conversation?

• i dont get how he turned 550 and 450 into -100 then turned it into 137
• He Subtracted those two number and got - 100
• why did you multiplied the 100 by 3 so it become 300 ?
• the comments are turning into Reddit 2.0 with the off topic conversations and the upvotes am I right? (upvote if u think im right)
• I got 100% on the math lesson that my teacher gave me before.
• this problem 1/2 −60%−25% should solve as in i have half pizza, i eat 60% of that half, then i eat 25% of whats left so i still have 0.15 of that half pizza.
why does Sal turn it into 0.5−0.6−0.25=−0.35 as the solution? and how do i know when to solve it one way and when to solve the other way?
• Well, if 1∕2 represents half a pizza, then 60% of half a pizza would be equal to 60%∙(1∕2)

But, we don't have 60%∙(1∕2), we have 60%, which we can write as 60%∙1 = 60% of a whole pizza.

And of course, taking away 60% of a pizza from half a pizza lands us at −10% of a pizza.
Taking away another quarter pizza leaves us with −35% of a pizza.
• I think Sal was having some problems here 😂
• this didnt make sense make it make sense!