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Question

Given 17 × 29 = 493, then 170 × 0.029 = ?

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is

4.93

Understanding Decimal Multiplication and Scaling

The question provides a known multiplication fact: $17 \times 29 = 493$. We are then asked to find the result of a similar multiplication: $170 \times 0.029$. This problem tests our understanding of how multiplying or dividing numbers by powers of 10 affects the product in multiplication.

Let's break down the relationship between the two multiplication problems:

  • The first number in the second problem is $170$. This is related to $17$ from the first problem. Specifically, $170 = 17 \times 10$.
  • The second number in the second problem is $0.029$. This is related to $29$ from the first problem. To get $0.029$ from $29$, we need to move the decimal point three places to the left. This is equivalent to dividing by $1000$, or multiplying by $0.001$. So, $0.029 = 29 \times 0.001$.

Calculating the New Product

Now, let's substitute these relationships into the second multiplication problem:

We want to calculate $170 \times 0.029$.

Substitute the relationships we found:

$(17 \times 10) \times (29 \times 0.001)$

Using the associative and commutative properties of multiplication, we can rearrange the terms:

$(17 \times 29) \times (10 \times 0.001)$

We already know that $17 \times 29 = 493$. So, we can substitute this value:

$493 \times (10 \times 0.001)$

Now, let's calculate the value of $10 \times 0.001$. When you multiply by 10, you move the decimal point one place to the right.

$10 \times 0.001 = 0.010 = 0.01$

So, the problem simplifies to:

$493 \times 0.01$

Multiplying a number by $0.01$ is the same as dividing it by $100$. This means we need to move the decimal point in $493$ two places to the left.

The number $493$ can be thought of as $493.0$. Moving the decimal point two places to the left gives us $4.93$.

Therefore, $170 \times 0.029 = 4.93$.

Step-by-Step Solution for Decimal Multiplication

Here is a summary of the steps:

  1. Start with the known fact: $17 \times 29 = 493$.
  2. Identify the numbers in the problem to be solved: $170$ and $0.029$.
  3. Compare these numbers to the original numbers ($17$ and $29$) in terms of powers of 10.
    • $170 = 17 \times 10$
    • $0.029 = 29 \times 0.001$ (or $29 \div 1000$)
  4. Rewrite the new multiplication problem using these relationships: $(17 \times 10) \times (29 \times 0.001)$.
  5. Rearrange the terms: $(17 \times 29) \times (10 \times 0.001)$.
  6. Substitute the known product: $493 \times (10 \times 0.001)$.
  7. Calculate the product of the powers of 10: $10 \times 0.001 = 0.01$.
  8. The problem becomes: $493 \times 0.01$.
  9. Perform the final multiplication: $493 \times 0.01 = 4.93$.

This result matches one of the given options.

Conclusion

Based on the calculations, $170 \times 0.029 = 4.93$. This demonstrates how understanding the relationship between multiplication and division by powers of 10 simplifies complex-looking problems when a related base calculation is provided.

Revision Table: Decimal Operations

Here's a quick review of decimal point movement with powers of 10:

Operation Multiplier/Divisor Decimal Point Movement
Multiply $10$ 1 place right
Multiply $100$ 2 places right
Multiply $0.1$ (or $1/10$) 1 place left
Multiply $0.01$ (or $1/100$) 2 places left
Divide $10$ 1 place left
Divide $100$ 2 places left
Divide $0.1$ 1 place right
Divide $0.01$ 2 places right

Additional Information: Properties of Multiplication

The solution used properties of multiplication to simplify the calculation. It's helpful to remember these properties:

  • Commutative Property: The order of factors does not change the product. $a \times b = b \times a$.
  • Associative Property: The grouping of factors does not change the product. $(a \times b) \times c = a \times (b \times c)$.
  • Identity Property: Any number multiplied by 1 is the number itself. $a \times 1 = a$.
  • Zero Property: Any number multiplied by 0 is 0. $a \times 0 = 0$.

In our solution, we used the commutative and associative properties to regroup the factors $(17 \times 10) \times (29 \times 0.001)$ into $(17 \times 29) \times (10 \times 0.001)$. This allowed us to use the given information ($17 \times 29 = 493$) directly.

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Similar Questions

  1. If 19 × 23 = 437, then find the value of (190 × 0.023).

  2. \(0.02\overline {45}\) written as a vulgar fraction in its simplest from is:
  3. 1.004 - 0.4 is equal to:

  4. 23 × 19 = 437. How much is 0.0437 ÷ 1.9 = ?

  5. Solve the following:

    196 – 19.6 – 1.96 – 0.196 = ?
  6. From a 50 m long steel bar, a workman has to cut off as many 5.25 m long pieces as possible. What decimal fraction of the whole will be left?

  7. If 123 × 356 = 43788, then 1.23 × 0.356 = ?

  8. The product of two numbers is 0.432. One of the numbers is 1.6. What is the other number?

  9. If 493 ÷ 29 = 17, then 4.93 ÷ 0.0017 = ?

  10. The product of two decimals is 0.768. If one of the decimal number is 1.6, find the other.


Important Questions from Decimals

  1. What is the result when 0.129129129… is converted to a fraction?

  2. Which of the following statement(s) is/are correct?

    I. (3/11) > 0.3

    II. (7/8) > 0.86

  3. The value of \(1.\overline{3}+0.\overline{69}-0.5\overline{23}\)  is equal to:

  4. The value of \(0.\bar 4 + 0.5 \bar 9 - 0.4 \overline{23}\)  is equal to:

  5. If 19 × 23 = 437, then find the value of (190 × 0.023).

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