Question 990949: Grade 7 question:
I am a two-digit prime number
I am one less than a multiple of 10
If you add 30 to me you get another prime number
Who am I
Answer by rothauserc(4718)   (Show Source):
You can put this solution on YOUR website! The two-digit prime numbers are 11, 13, 17, 19, 23, 29, 31, 27, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97
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The two-digit prime numbers that are one less than a multiple of ten are 19, 29, 59, 79 and 89
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now we add 30 to each prime number
19 + 30 = 49 is NOT a prime
29 + 30 = 59 IS a prime number
59 + 30 = 89 IS a prime number
79 + 30 = 109 IS a prime number
89 + 30 = 119 is NOT a prime number
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29, 59, 79 satisfy the criteria
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