Megha is using the Sieve of Eratosthenes on the numbers 1 to 50. She has finished the first four rows (primes circled, the rest crossed out). How many prime numbers are there in the orange row?

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3. In 41 to 50 the primes are 41, 43 and 47, so there are 3. 45 = 5 × 9 and 49 = 7 × 7 are odd but not prime; 42, 44, 46, 48, 50 are even.

Megha is using the Sieve of Eratosthenes on the numbers 1 to 50. She has finished the first four rows (primes circled, the rest crossed out). How many prime numbers are there in the orange row?

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