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Beth is given the following question - OCR - GCSE Maths - Question 22 - 2017 - Paper 1

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Beth is given the following question. Work out $4.1 \times 10^5 \times 3 \times 10^2$. Give your answer in standard form. This is Beth's answer to the question. ... show full transcript

Worked Solution & Example Answer:Beth is given the following question - OCR - GCSE Maths - Question 22 - 2017 - Paper 1

Step 1

Explain why Beth's answer is incorrect.

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Answer

To solve the expression 4.1×105×3×1024.1 \times 10^5 \times 3 \times 10^2, first, we multiply the coefficients and then add the exponents of the powers of 10.

  1. Multiply Coefficients:

    4.1×3=12.34.1 \times 3 = 12.3

  2. Add Exponents:

    105×102=105+2=10710^5 \times 10^2 = 10^{5+2} = 10^7

So, the correct calculation gives:

12.3×10712.3 \times 10^7

Beth's answer appears to be accurate at first, but the common mistake she made might be related to the placement of the decimal point when converting to standard form. If her final result is presented without normalizing (keeping the coefficient between 1 and 10), it would be inaccurate. Thus her answer should be presented as:

1.23×1081.23 \times 10^8.

Step 2

Show that $4.5 \times 10^2 + 7.3 \times 10^3 = 7.75 \times 10^3$.

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Answer

To show the equation, we first need to express 4.5×1024.5 \times 10^2 in terms of 10310^3:

  1. Convert the term:

    4.5×102=0.45×1034.5 \times 10^2 = 0.45 \times 10^3

  2. Add the two terms:

    0.45×103+7.3×103=(0.45+7.3)×1030.45 \times 10^3 + 7.3 \times 10^3 = (0.45 + 7.3) \times 10^3

    =7.75×103= 7.75 \times 10^3

Thus, we have shown that 4.5×102+7.3×103=7.75×1034.5 \times 10^2 + 7.3 \times 10^3 = 7.75 \times 10^3.

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