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.

### Course: Digital SAT Math>Unit 7

Lesson 2: Unit conversion: medium

# Units — Basic example

Watch Sal work through a basic Units problem.

## Want to join the conversation?

• cant I just know there is 150mg in 15l so 3/4 * 150 = 112.5mg

we Asians got our own trick

I'm from Nepal
• so luckyyy
• Couldn't you just do 15*10 to get 150 and then choose the first one because if it is 3/4 then it will have to less than 150 and the only choice that is less than 150 is choice A
• There are more than one way to solve a problem. As long as the answer is right and you understand what you're doing, you should be fine.
• this example was easy to understand and easy to learn
• Why does 7.5 mg/L multiply 15L? I don't understand that part.
• You have 15 liters. 3/4 of 10 mg/L is 7.5 mg/L (milligrams per liter).

In other words, for every liter you have 7.5 milligrams of nitrite, so multiply 7.5 by 15 to find how many milligrams of nitrite are found in 15 liters.

7.5 mg/L * 15L = 112.5 mg
• Couldn't you just do 15*10 to get 150 and then choose the first one because if it is 3/4 then it will have to less than 150 and the only choice that is less than 150 is choice A
• That's what I did lol
• he forgot to say test takers you got this
• why do we keep the units when we know what our final units are
• Keeping the units is an easy way to see if you mix up the equation. For example, if you keep the units and end up with L/mg, you immediately know that you messed up, whereas without units, you might not catch that mistake.
• anyone can explain me this example ??