What is 1.5 (One and a Half)?

S1-SA2-0830

Grade Level:

Class 4

Maths, Finance, Science, Computing, AI

Definition

What is it?

1.5, also read as "one and a half," is a number that combines a whole number (1) and a fraction (0.5 or 1/2). It means you have one complete unit and half of another unit. It sits exactly in the middle of 1 and 2 on a number line.

Simple Example

Quick Example

Imagine you have one full roti and your friend gives you half of another roti. Together, you have 1.5 rotis. It's more than one full roti but less than two full rotis.

Worked Example

Step-by-Step

Let's say a recipe needs 1.5 cups of milk. How much milk is that?
Step 1: Understand "1.5" means "1 whole" and "0.5 (half)".
---Step 2: Take 1 full cup of milk.
---Step 3: Now, for the "0.5" part, take half of another cup. You can do this by filling a cup halfway.
---Step 4: Combine the 1 full cup and the half cup.
---Step 5: So, 1.5 cups of milk is one full cup plus half of another cup.

Why It Matters

Understanding 1.5 helps you manage money, measure ingredients for cooking, and even understand sports scores. People in finance, engineering, and data science use such numbers every day for precise calculations. It's a basic building block for understanding decimals and fractions.

Common Mistakes

MISTAKE: Thinking 1.5 is the same as 1 and 5. | CORRECTION: 1.5 means 1 whole and 5 tenths (or half). The point separates the whole part from the fractional part.

MISTAKE: Confusing 1.5 with 15. | CORRECTION: 1.5 is much smaller than 15. The decimal point makes a big difference; it shows a value between 1 and 2.

MISTAKE: Believing 1.5 is a whole number. | CORRECTION: 1.5 is a decimal number, meaning it has a fractional part (the .5) in addition to a whole part (the 1).

Practice Questions

Try It Yourself

QUESTION: If a bus journey takes 1.5 hours, how many minutes is that? | ANSWER: 90 minutes (1 hour = 60 minutes, 0.5 hour = 30 minutes. 60 + 30 = 90).

QUESTION: You bought 1.5 kg of apples. Your friend bought 2 kg. Who bought more apples and by how much? | ANSWER: Your friend bought more apples, by 0.5 kg.

QUESTION: A tailor needs 1.5 meters of cloth for one shirt. How much cloth will he need for two shirts? | ANSWER: 3 meters (1.5 + 1.5 = 3).

MCQ

Quick Quiz

Which of these correctly represents 1.5?

One whole and five wholes

One whole and half of another whole

Fifteen wholes

One and five-tenths of a whole

The Correct Answer Is:

Option B correctly describes 1.5 as one whole and half of another whole. Option D is also technically correct, but B is simpler for this grade. Options A and C are incorrect as they misunderstand the decimal point.

Real World Connection

In the Real World

When you buy vegetables, the vendor might weigh out 1.5 kg of potatoes. When booking a cab, the app might show your destination is 1.5 km away. Even in cricket, a bowler might bowl 1.5 overs, meaning one full over and half of the next over. These everyday situations show how important 1.5 is.

Key Vocabulary

Key Terms

DECIMAL: A number that includes a whole part and a fractional part, separated by a decimal point. | WHOLE NUMBER: A number without fractions or decimals (like 1, 2, 3). | FRACTION: A part of a whole (like 1/2 or 0.5). | HALF: One of two equal parts of something. | TENTHS: The first digit after the decimal point, representing parts out of ten.

What's Next

What to Learn Next

Now that you understand 1.5, you can explore other decimal numbers like 2.5 or 0.75. You can also learn about converting fractions to decimals and vice versa. This will help you measure things more accurately and solve more complex problems.