prealgebra – Math On The Fly

Tag: prealgebra

Pre-Algebra & Math Basics: Divisibility Rules

Posted on March 23, 2025March 23, 2025 by Nathaniel

In the math video, divisibility rules is covered. Divisibility rules are shortcuts that allow us to quickly figure out if a number divides evenly into another whole number. This skill can be used for reducing fractions, finding factors of numbers, finding the GCF, factoring polynomials, simplifying square roots and much more. Most students know the divisibility rule for 2 (the number must be even), the rule for 5 (the number must end in 0 or 5) and the rule for 10 (the number must end in 0). I cover all the divisibility rules from 1 to 10. Without using a calculator, you will be able to easily tell for example, if 3 divides evenly into 1,232,251 or if 4 divides evenly into a number like 5,385,414.

This topic is usually covered one time in middle school, and then it is never covered again. Some school systems never cover the topic at all, which I think is ridiculous. All of the rules can be proven algebraically through modular arithmetic, which is an area of mathematics that is usually only covered in math competitions or accelerated math classes. We will simply cover the shortcuts.

We cover the following problems in the video:

→ Are 8 and 5397 divisible by 1?
→ Are 3516 and 2847 divisible by 2?
→ Are 24, 6702 and 3335 divisible by 3?
→ Are 5916, 7508, 4442, 61592 and 37900 divisible by 4?
→ Are 4830, 1965 and 50502 divisible by 5?
→ Are 2574, 9128, 4920 and 5133 divisible by 6?
→ Are 364, 717, 105 and 3546 divisible by 7?
→ Are 4800, 39056, 6009, 17078, 450388 and 21000 divisible by 8?
→ Are 36, 7425 and 9199 divisible by 9?
→ Are 9170, 1005 and 80002 divisible by 10?

Below is the video. Enjoy!

Pre-Algebra & Math Basics: Rounding Decimals

Posted on March 23, 2025 by Nathaniel

In this video, I cover the topic of rounding decimals, a topic that confuses many students. I cover the 3 steps of rounding decimals and use those steps to round decimals to the nearest tenth, hundredth, thousandth and ten thousandth. I also cover the special situations of rounding up on 9, rounding to the nearest dollar and whole number, as well as rounding repeating decimals.

The following problems are covered in the video:

→ Round 8.2748 and 0.9468 to the nearest tenth
→ Round 0.1652 and 6.083 to the nearest tenth
→ Round 1.3975 to the nearest hundredth (Round up on 9)
→ Round 7.615 and 0.8016 to the nearest thousandth
→ Round 9.1738 to one, two, three and four decimal places
→ Round 3.499 and 49.82 to the nearest whole number
→ Round $7.61 to the nearest dollar
→ Round $24.19 to the nearest dollar

The following examples of repeating decimals are also covered:

Below is the video. Enjoy!

For this ACT Math post, we are going to delve briefly into number theory. On every ACT test, you are going to see problems related to either factors, multiples, primes, or a combination of all three types of numbers. We cover a basic example that involves finding factors of numbers, as well as recognizing prime numbers.

The example used in the video will be based off the following ACT math problem below:

Click here to see the problem.

This is the practice exercise we will work out in the video:

This practice problem is considered an EASY to MEDIUM difficulty problem.

Pre-Algebra ACT Math Prep: Combining Ratios

Posted on June 26, 2024March 12, 2025 by Nathaniel

Pre-Algebra ACT Math Prep: Fractions of Amounts

Posted on June 25, 2024March 12, 2025 by Nathaniel

For this ACT math post, we will be covering prealgebra and finding fractions of amounts. Even though working out fractions of groups by hand is simple compared to other concepts, we aid in understanding the concept better by showing the problem worked out by hand, as well as with pictures.

The example used in the video will be based off the following ACT math problem below:

Click here to see the problem.

This is the practice exercise we will work out in the video:

This practice problem is considered an EASY difficulty problem.