gallons collected.  gallons short.

To convert between minutes and hours, you can use dimensional analysis to ensure that you are performing the right calculations. You know that there are 60 minutes for every 1 hour, and you start with minutes and need to get your answer in terms of hours. That means that you want to set up the equation so that the units "minutes" cancels and leaves you with just "hours":

You can see here that "minutes" is in both numerator and denominator, allowing you to cancel those units.  And it dictates that to get your answer you'll divide 450 by 60.  That reduces as a fraction to 45 divided by 6, which comes out to 7.5.

When converting between units, it can be helpful to use dimensional analysis to set up your equation. You know that there are 12 inches in 1 foot, and that you need to convert 18 feet to a number of inches. If you then structure your math so that the units cancel via division, you can ensure that you're making the right "do I multiply or do I divide by 12" decision:

Helps you determine that you need to multiply, because then the "feet" units cancel leaving you with the units you want, which is inches.  This means you multiply 18 by 12, which gives you 216 inches.

A great way to ensure you make the proper "do I multiply or divide?" decision on any conversion problem is to use dimensional analysis, which means to set up the units in your calculation so that the units you don't want in your answer cancel, and the unit(s) you do want in your answer remain. Here you're given gallons and asked to convert to quarts, so you want to set up the math so that gallons cancels. That means you'll use:

This preserves the ratio of 4 quarts to every 1 gallon, and allows the unit "gallons" to cancel via division, so that you're left with quarts. That also means that you multiply 8 by 4 to get the answer, 32.

When you're working with conversion problems, it is helpful to use dimensional analysis to make sure that you're making the proper "do I multiply or divide by this conversion" decision. Here you're given a number of miles (she wants to ride 20 miles) and you need to get to kilometers. So you can structure your math with miles in the denominator of the fraction, and that means that the units "miles" will cancel leaving you with just "kilometers":

As you can see, this tells you to divide by 0.62, and when you've cancelled the unit "miles" you're left with just "kilometers." Note, also, that the question asks for an estimate ("which of the following is closest") so you can safely divide by just 0.6, or 3/5, to get to 33.33, and the only answer that is close is 32.

When you're working with conversion problems, it is helpful to use dimensional analysis to ensure that you are properly applying the conversion (i.e. "should I multiply or divide?"). Here you're given a number of steps and you need to convert to miles using the conversion 2,500 steps = 1 mile. You can then set up your math so that the unit "steps" cancels and you're left with just "miles."  That would mean:

As you can see, steps will cancel due to division, meaning that you'll divide 320,000 by 2,500 and be left with the proper unit miles.  To do this math by hand, you should also see that you can factor out 100 from both 320,000 and 2,500, leaving you with the problem 3200 divided by 25.  This leads you to the correct answer, 128.

Whenever you're workin with unit conversions, it is a good idea to use dimensional analysis to structure your math to help you choose the right operation (multiply vs. divide). This means that you'll set up your equation to cancel the units that you don't want in your answer, and therefore you'll be left with the proper units. Here you're given inches and asked to convert to centimeters, so you'll set up the math with inches in the denominator so that the units cancel:

This means that you'll multiply 10 by 2.54, and the inch units will cancel ensuring that you're properly converting to centimeters. 10 times 2.54 is 25.4, which rounds to 25.

Whenever you're working with unit conversions, it is a good idea to use dimensional analysis to ensure that you are setting up your calculation - specifically the choice of whether you multiply or divide by the conversion ratio - properly. This means that you'll set up the math so that the units you're given cancel, leaving you with the units you need to arrive at in the end. Here you're given kilograms and want to get to pounds, so you'll multiply by a conversion with kilograms in the denominator so that kilograms cancel, leaving you with pounds:

This means that you multiply 25 by 2.2, and that kilograms cancel and the only unit left is the one you want, pounds.  25 times 2.2 is 55, giving you the correct answer.

Whenever you're working with unit conversions, it is a good idea to use dimensional analysis to structure your math properly - specifically as it pertains to the question of whether you should multiply or divide by the conversion ratio provided. That means you'll set up the math so that the units you don't want cancel, leaving you with the units you do. Here you're given pints and asked to arrive at quarts, so you'll set up your math such that pints is in the denominator of the conversion ratio so that it cancels. That means that your math will look like:

This means you'll divide 16 by 2 to get your answer, and since pints cancels via division, you know that you've converted properly to quarts.  16 divided by 2 is 8, making 8 the correct answer.