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10 (a) Show that 95 is not a prime number - OCR - GCSE Maths - Question 10 - 2023 - Paper 6

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10 (a) Show that 95 is not a prime number. (b) (i) 2000 and 8750 are written below as the product of their prime factors. 2000 = 2² × 5³ 8750 = 2 × 5⁵ × 7 Find th... show full transcript

Worked Solution & Example Answer:10 (a) Show that 95 is not a prime number - OCR - GCSE Maths - Question 10 - 2023 - Paper 6

Step 1

Show that 95 is not a prime number.

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Answer

To determine if 95 is a prime number, we need to check if it has any positive divisors other than 1 and itself. The number 95 can be divided by 1, 5, 19, and 95. Since 95 has divisors other than 1 and 95 (specifically, 5 and 19), it is not a prime number.

Step 2

Find the highest common factor (HCF) of 2000 and 8750.

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Answer

To find the HCF, we first identify the prime factors of the numbers:

  • The prime factorization of 2000 is given as: 2000=22×532000 = 2^2 × 5^3
  • The prime factorization of 8750 is given as: 8750=21×55×78750 = 2^1 × 5^5 × 7

Next, we take the lowest power of each common prime factor:

  • For the prime factor 2: the minimum power is extmin(2,1)=1 ext{min}(2, 1) = 1
  • For the prime factor 5: the minimum power is extmin(3,5)=3 ext{min}(3, 5) = 3

Thus, the HCF is given by:

HCF=2extmin(2,1)×5extmin(3,5)=21×53=2×125=250HCF = 2^{ ext{min}(2, 1)} × 5^{ ext{min}(3, 5)} = 2^1 × 5^3 = 2 × 125 = 250

Step 3

Write 2 × 10¹² as a product of its prime factors.

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Answer

First, we will factorize 10:

10=2×510 = 2 × 5

Thus, we can write:

2×1012=2×(2×5)122 × 10^{12} = 2 × (2 × 5)^{12}

This expands to:

2×212×512=21+12×512=213×5122 × 2^{12} × 5^{12} = 2^{1 + 12} × 5^{12} = 2^{13} × 5^{12}

So, the final prime factorization is:

213×5122^{13} × 5^{12}

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