Capítulo 1 de 524% del examen
Basic Math for the HESI A2
The math section of the HESI A2 tests the everyday arithmetic that nurses use for measurements, dosages, and record keeping. You will work with fractions, decimals, ratios and proportions, percentages, and unit conversions. This chapter reviews each skill with clear, repeatable steps so you can solve problems quickly and accurately without a calculator.
Working with Fractions
A fraction shows a part of a whole, with a numerator on top and a denominator on the bottom. To add or subtract fractions you must first give them a common denominator, while multiplying and dividing follow their own rules. Reducing answers to lowest terms is expected on the exam.
Common denominator for add/subtract
Rewrite each fraction with the least common denominator, then add or subtract only the numerators and keep the denominator the same.
Multiply straight across
To multiply fractions, multiply the numerators together and the denominators together, then reduce the result.
Divide by the reciprocal
To divide by a fraction, flip the second fraction and multiply. For example, 3/8 divided by 1/2 equals 3/8 times 2/1.
Reduce to lowest terms
Divide the numerator and denominator by their greatest common factor so the final answer is fully simplified.
Decimals and Place Value
Decimals are another way to write parts of a whole using place values of tenths, hundredths, and thousandths. Lining up decimal points is the key to adding and subtracting correctly. Rounding is often required to report a clean answer.
Align the decimal points
When adding or subtracting, stack the numbers so the decimal points line up, adding zeros as placeholders if needed.
Count decimal places when multiplying
Multiply as whole numbers, then place the decimal point so the product has as many decimal places as the two factors combined.
Move the decimal when dividing by a decimal
Shift the decimal in the divisor to make it a whole number and move the dividend's decimal the same number of places.
Round using the next digit
To round, look at the digit just to the right of the target place. If it is 5 or more, round up; if it is less than 5, round down.
Ratios and Proportions
A ratio compares two quantities, and a proportion states that two ratios are equal. Nurses use proportions constantly to scale recipes, mix solutions, and calculate rates. Cross multiplication is the fastest way to solve for an unknown.
Write ratios consistently
Keep the same order of comparison on both sides of a proportion, such as nurses to patients on both the left and right.
Cross multiply to solve
In a/b = c/d, multiply a by d and b by c, set them equal, then solve for the unknown.
Use unit rates
Divide to find how much of one quantity corresponds to a single unit of another, such as miles per gallon.
Check that units match
Make sure the labels line up correctly so you compare like quantities, such as milligrams with milligrams.
Percentages
A percent expresses a number out of one hundred and appears in discounts, dosages, and statistics. You should be able to move fluidly between percents, decimals, and fractions. Percent increase and decrease problems compare a change to the original amount.
Percent to decimal
Divide a percent by 100, or move the decimal point two places to the left, so 25% becomes 0.25.
Find a percent of a number
Convert the percent to a decimal and multiply, so 25% of 80 equals 0.25 times 80, which is 20.
Percent one number is of another
Divide the part by the whole and multiply by 100, so 15 out of 60 is 25%.
Percent change
Divide the amount of change by the original value, then multiply by 100 to get percent increase or decrease.
Measurement Conversions
Nurses must convert between metric units and between household and metric measures. Knowing a few key equivalents lets you set up conversions with confidence. Temperature conversions between Celsius and Fahrenheit also appear on the exam.
Metric prefixes shift by 1000
There are 1000 milligrams in a gram, 1000 grams in a kilogram, and 1000 milliliters in a liter.
Pounds to kilograms
Divide pounds by 2.2 to get kilograms, since one kilogram equals about 2.2 pounds.
Celsius to Fahrenheit
Multiply the Celsius temperature by 9/5 and add 32, so 37 degrees Celsius equals 98.6 degrees Fahrenheit.
Set up dimensional analysis
Write conversion factors as fractions so unwanted units cancel and the desired unit remains.
Pon a prueba tus conocimientos
Preguntas de práctica sobre Basic Math for the HESI A2