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On January 1, Jamie did one sit-up. On each of the next 364 days, she
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11 May 2021, 03:43
11 May 2021, 03:43
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On January 1, Jamie did one sit-up. On each of the next 364 days, she did one more than on the previous day. What was the total number of sit-up she did in 365 days?
(A) 66430
(B) 66795
(C) 66978
(D) 67160
(E) 132860
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
(A) 66430
(B) 66795
(C) 66978
(D) 67160
(E) 132860
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
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Re: On January 1, Jamie did one sit-up. On each of the next 364 days, she
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11 May 2021, 05:48
11 May 2021, 05:48
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Carcass wrote:
On January 1, Jamie did one sit-up. On each of the next 364 days, she did one more than on the previous day. What was the total number of sit-up she did in 365 days?
(A) 66430
(B) 66795
(C) 66978
(D) 67160
(E) 132860
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
(A) 66430
(B) 66795
(C) 66978
(D) 67160
(E) 132860
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
Day 1: 1 sit-up
Day 2: 2 sit-ups
Day 3: 3 sit-ups
Day 4: 4 sit-ups
.
.
.
Day 365: 365 sit-ups
So, we want the sum 1 + 2 + 3 + 4 + . . . 364 + 365
We have a nice formula for the sum of the first n positive integers.
It goes like this: 1 + 2 + 3 + . . . + n = (n)(n + 1)/2
So, 1 + 2 + 3 + 4 + . . . 364 + 365 = (365)(365 + 1)/2
= (365)(366)/2
= (365)(183)
STOP! Before you calculate (365)(183), check the answer choice to see if you can avoid this tedious calculation.
Examine the units digits of (365)(183)
Since 5 x 3 = 15, the units digit of (365)(183) will be 5
Only answer choice B meets this condition, so it must be the correct answer.
gmatclubot
Re: On January 1, Jamie did one sit-up. On each of the next 364 days, she [#permalink]
11 May 2021, 05:48
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