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Re: What is the units digit of the product of the first 50 primes? [#permalink]
PareshGmat wrote:
Answer = A.) 0

Just write down the first 4 prime numbers & we get the answer

1*2*3*5 ............ and so on... will end up with 0 in units place

Similar question......

What is the units digit of the product of the first 100 even numbers?

2*4*6*8*10 ............. will end up in 0 in the units place

What is the units digit of the product of the first 100 odd numbers?

1*3*5*7 ................... will end up in 5 in the units place

Experts: Are these potential GMAT questions.... ??


Prime starts from 2 not from 1 .. . . .
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Re: What is the units digit of the product of the first 50 primes? [#permalink]
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Hi All,

On Test Day, sometimes the biggest clue/shortcut will be in how the answer choices are written.

We're asked to think about the PRODUCT of the first 50 prime numbers. We clearly are NOT expected to do all of that math, so there MUST be a pattern that we can use to get to the correct answer.

Since the first prime is "2", the product of all of those primes MUST be EVEN. Considering how THESE answers are written, only one answer matches...

Final Answer:

GMAT assassins aren't born, they're made,
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Re: What is the units digit of the product of the first 50 primes? [#permalink]
no need to count. All primes are odd and multiplying by 2 (only even prime) we get even

Only A fits
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Re: What is the units digit of the product of the first 50 primes? [#permalink]
Product of 50 primes
2 , 3 , 5 , 7 ...
2x5 = 10
A
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Re: What is the units digit of the product of the first 50 primes? [#permalink]
That can be one way to solve: 2*5=10
So no matter what the other nos. are the answer will end with 0 at unit's place.

I solved it using the power of even numbers.

Even is there is one even no. in the list, then the product will be even and luckily 2 is part of the list.
Only even choice is 0.
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Re: What is the units digit of the product of the first 50 primes? [#permalink]
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Re: What is the units digit of the product of the first 50 primes? [#permalink]
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