Rate, Distance, Time - Problem, 6

Category: Algebra, Mechanics, Physics

"Published in Newark, California, USA"

The local train is 25 miles down the track from Central Station when the express leaves the station. The local train travels at a rate of 50 mi/hr and the express travels travels at a rate of 80 mi/hr. Let n represent the number of hours since the express train left Central Station.

(a) Write an expression that represents the express train's distance from Central Station in n hours.

(b) When will the express train catch up with the local train?

Solution:

To illustrate the problem, it is better to draw the figure as follows

Photo by Math Principles in Everyday Life

Initially, the local train is already left from Central Station which is 25 miles apart. The time traveled by the local train is

 

 

   
If the express train leaves from Central Station which is faster than the local train, then the express train will catch up the local train at time n.

Photo by Math Principles in Everyday Life

(a) The distance traveled by the express train is
 

 

 

 

 
(b) Finally, the express train will catch up the local train at
 

 

 

 

 

 

 

 

or

Divisibility - 4

Category: Arithmetic

"Published in Newark, California, USA"

Divisibility by 4:

How do you know that a number is divisible by 4? Well, a number is divisible by 4 if the last two digits of a number are multiples of 4 or divisible by 4. Also, if the last two digits of a number are 0. You need to remember or memorize the multiplication table for this one.  

Example 1:

The first thing that we need to do is to inspect the given number if it is divisible by 4 or not. Let's examine the last two digits of a given number which is 82. 

Since 82 is not a multiple of 4, then the given number is not divisible by 4. We know that 80 is divisible by 4. There's a remainder of 2 in the division. The answer or a quotient must be a whole number itself. You should not have a fraction or a remainder in the final answer. 

Example 2:

 
The first thing that we need to do is to inspect the given number if it is divisible by 4 or not. Let's examine the last two digits of a given number which is 48. 

Since 48 is a multiple of 4, then the given number is divisible by 4. There's no remainder or a fraction in the division.

Example 3:

The first thing that we need to do is to inspect the given number if it is divisible by 4 or not. Since the last two digits of a given number are 0, then the given number is divisible by 4. There's no remainder or a fraction in the division.

You should consider in studying the divisibility of a number because you will use these principles later when you will study higher Math subjects that involves the division of a number, simplifying fractions, and even factoring. 

This method can also be used for negative integers as long as the last two digits are multiples of 4 or 0. Again, there should be no remainder or a fraction in the division. 
 

Divisibility - 3

Category: Arithmetic

"Published in Newark, California, USA"

Divisibility by 3:

How do you know that a number is divisible by 3? Well, a number is divisible by 3 if the sum of the digits are divisible by 3 or multiples of 3. You need to remember or memorize the multiplication table for this one.

Example 1:

The first thing that we need to do is to inspect the given number if it is divisible by 3 or not. Let's add the digits as follows

You can add the digits again as follows

Since 4 is not a multiple of 3, then the given number is not divisible by 3. There's a remainder of 1 in the division. The answer or a quotient must be a whole number itself. You should not have a fraction or a remainder in the final answer.

Example 2:

The first thing that we need to do is to inspect the given number if it is divisible by 3 or not. Let's add the digits as follows

You can add the digits again as follows

 

Since 9 is a multiple of 3, then the given number is divisible by 3. There's no remainder or a fraction in the division.

You should consider in studying the divisibility of a number because you will use these principles later when you will study higher Math subjects that involves the division of a number, simplifying fractions, and even factoring. 

This method can also be used for negative integers as long as the sum of the digits is a multiple of 3. Again, there should be no remainder or a fraction in the division.