Express seventeen tens in standard unit form by writing the equivalent number in terms of hundreds, tens, and ones.

Introduction / Context:
This question belongs to basic place value and unit form concepts in arithmetic. Understanding how tens, hundreds, and ones relate is fundamental in primary mathematics and is often revisited in aptitude tests to ensure that candidates have a clear mental model of our base ten number system. Here we are asked to convert seventeen tens into a standard expanded form that explicitly shows hundreds, tens, and ones.

Given Data / Assumptions:
- We are working in the base ten number system.
- One ten is equal to ten ones.
- Ten tens equal one hundred.
- The phrase seventeen tens means 17 groups of ten, which must be rewritten in standard unit form as hundreds, tens, and ones.

Concept / Approach:
The base ten system organizes numbers into powers of ten: ones, tens, hundreds, thousands, and so on. Each place is ten times the value of the place to its right. To convert seventeen tens into standard form, we first convert tens into an equivalent number of ones, obtain the overall number, and then express that number back into hundreds, tens, and ones. Recognizing when a collection of tens can be regrouped into hundreds is the main idea tested here.

Step-by-Step Solution:
Step 1: Interpret the phrase seventeen tens as 17 multiplied by 10 because each ten is a group of 10 ones. Step 2: Compute 17 * 10 = 170. This means seventeen tens are equal to 170 ones. Step 3: Now we express 170 in standard place value form. The number 170 has digits 1, 7, and 0, reading from left to right as hundreds, tens, and ones. Step 4: The digit 1 in the hundreds place represents 1 hundred, which equals 100. Step 5: The digit 7 in the tens place represents 7 tens, which equals 70. Step 6: The digit 0 in the ones place represents 0 ones, so there are no single units left over. Step 7: Therefore, seventeen tens can be written as 1 hundred, 7 tens, and 0 ones in unit form.

Verification / Alternative check:
We can verify by expanding the standard unit form back into a single number. One hundred plus seventy plus zero equals 100 + 70 + 0 = 170. This matches the earlier calculation of 17 * 10. Another way to check is to imagine grouping ten tens into a hundred: from seventeen tens, ten tens form one hundred, and seven tens remain. That gives 1 hundred and 7 tens, exactly the structure in the correct option. Since both methods give the same result, we can be confident in the answer.

Why Other Options Are Wrong:
Option 17 ones: This corresponds to the number 17, which would be 1 ten and 7 ones, not seventeen tens.
Option 170 ones: This describes the total number of ones correctly but does not express the number in hundreds, tens, and ones unit form as required by the question.
Option 1 ten and 7 ones: This is the expanded form of 17, not of 170, so it represents seventeen ones, not seventeen tens.
Option 7 tens and 10 ones: Ten ones make 1 ten, so this combines to 8 tens or 80, which is far less than 170.

Common Pitfalls:
Learners sometimes confuse the phrases seventeen and seventeen tens, treating them as the same. Another common mistake is to stop at 170 ones without translating that into hundreds, tens, and ones. Some students may also mis-handle regrouping, for example thinking that 10 ones always stay as 10 ones instead of regrouping into 1 ten. Practising conversions in both directions, from unit form to standard form and back, helps reinforce these place value relationships.

Final Answer:
Seventeen tens in unit form is 1 hundred, 7 tens, and 0 ones.