Decimals are an important part of the mathematical world. They allow us to represent numbers that fall between whole numbers, giving us a more precise measurement or value. In Lesson 3, we explored how to read and write decimals, and in this answer key, we will go over the correct answers and explanations for each question. Let's dive in!

### Question 1: Write the decimal 0.35 in word form.

The correct answer is thirty-five hundredths. When writing decimals in word form, we read the whole number part first (if any), followed by the word "and", and then the decimal part. For 0.35, the whole number part is 0, and the decimal part is 35 hundredths. Therefore, the word form of 0.35 is thirty-five hundredths.

### Question 2: Write the decimal 4.02 in expanded form.

The correct answer is 4 + 0.02. In expanded form, we break down the decimal into its whole number and decimal parts. For 4.02, the whole number part is 4, and the decimal part is 0.02. Therefore, the expanded form of 4.02 is 4 + 0.02.

### Question 3: Write the decimal 0.064 in decimal form.

The correct answer is 0.064. When writing decimals in decimal form, we simply write the given decimal as it is. For 0.064, the decimal is already in decimal form, so the answer is 0.064.

### Question 4: Write the decimal 7.83 in word form.

The correct answer is seven and eighty-three hundredths. Following the same pattern as in question 1, we read the whole number part first, which is 7, followed by "and", and then the decimal part, which is 83 hundredths. Therefore, the word form of 7.83 is seven and eighty-three hundredths.

### Question 5: Write the decimal 0.6 in expanded form.

The correct answer is 0 + 0.6. In expanded form, we break down the decimal into its whole number and decimal parts. For 0.6, the whole number part is 0, and the decimal part is 0.6. Therefore, the expanded form of 0.6 is 0 + 0.6.

### Question 6: Write the decimal 0.045 in decimal form.

The correct answer is 0.045. Again, when writing decimals in decimal form, we write the given decimal as it is. For 0.045, the decimal is already in decimal form, so the answer is 0.045.

### Question 7: Write the decimal 9.724 in word form.

The correct answer is nine and seven hundred twenty-four thousandths. Following the same pattern as in question 1, we read the whole number part first, which is 9, followed by "and", and then the decimal part, which is 724 thousandths. Therefore, the word form of 9.724 is nine and seven hundred twenty-four thousandths.

### Question 8: Write the decimal 0.9 in expanded form.

The correct answer is 0 + 0.9. In expanded form, we break down the decimal into its whole number and decimal parts. For 0.9, the whole number part is 0, and the decimal part is 0.9. Therefore, the expanded form of 0.9 is 0 + 0.9.

### Question 9: Write the decimal 0.003 in decimal form.

The correct answer is 0.003. Once again, when writing decimals in decimal form, we write the given decimal as it is. For 0.003, the decimal is already in decimal form, so the answer is 0.003.

### Question 10: Write the decimal 6.025 in word form.

The correct answer is six and twenty-five thousandths. Following the same pattern as in question 1, we read the whole number part first, which is 6, followed by "and", and then the decimal part, which is 25 thousandths. Therefore, the word form of 6.025 is six and twenty-five thousandths.

### Question 11: Write the decimal 0.8 in expanded form.

The correct answer is 0 + 0.8. In expanded form, we break down the decimal into its whole number and decimal parts. For 0.8, the whole number part is 0, and the decimal part is 0.8. Therefore, the expanded form of 0.8 is 0 + 0.8.

### Question 12: Write the decimal 0.006 in decimal form.

The correct answer is 0.006. As mentioned before, when writing decimals in decimal form, we write the given decimal as it is. For 0.006, the decimal is already in decimal form, so the answer is 0.006.

### Question 13: Write the decimal 3.007 in word form.

The correct answer is three and seven thousandths. Following the same pattern as in question 1, we read the whole number part first, which is 3, followed by "and", and then the decimal part, which is 7 thousandths. Therefore, the word form of 3.007 is three and seven thousandths.

### Question 14: Write the decimal 0.5 in expanded form.

The correct answer is 0 + 0.5. In expanded form, we break down the decimal into its whole number and decimal parts. For 0.5, the whole number part is 0, and the decimal part is 0.5. Therefore, the expanded form of 0.5 is 0 + 0.5.

### Question 15: Write the decimal 0.001 in decimal form.

The correct answer is 0.001. Once again, when writing decimals in decimal form, we write the given decimal as it is. For 0.001, the decimal is already in decimal form, so the answer is 0.001.

### Question 16: Write the decimal 2.013 in word form.

The correct answer is two and thirteen thousandths. Following the same pattern as in question 1, we read the whole number part first, which is 2, followed by "and", and then the decimal part, which is 13 thousandths. Therefore, the word form of 2.013 is two and thirteen thousandths.

### Question 17: Write the decimal 0.07 in expanded form.

The correct answer is 0 + 0.07. In expanded form, we break down the decimal into its whole number and decimal parts. For 0.07, the whole number part is 0, and the decimal part is 0.07. Therefore, the expanded form of 0.07 is 0 + 0.07.

### Question 18: Write the decimal 0.02 in decimal form.

The correct answer is 0.02. As mentioned earlier, when writing decimals in decimal form, we write the given decimal as it is. For 0.02, the decimal is already in decimal form, so the answer is 0.02.

### Question 19: Write the decimal 5.009 in word form.

The correct answer is five and nine thousandths. Following the same pattern as in question 1, we read the whole number part first, which is 5, followed by "and", and then the decimal part, which is 9 thousandths. Therefore, the word form of 5.009 is five and nine thousandths.

### Question 20: Write the decimal 0.4 in expanded form.

The correct answer is 0 + 0.4. In expanded form, we break down the decimal into its whole number and decimal parts. For 0.4, the whole number part is 0, and the decimal part is 0.4. Therefore, the expanded form of 0.4 is 0 + 0.4.

That concludes the answer key for Lesson 3 on reading and writing decimals. Decimals are an important concept in mathematics, and being able to accurately read and write them is a valuable skill. By practicing these exercises and understanding the explanations provided, you can enhance your proficiency with decimals and further develop your mathematical abilities.