June 25, 1982, fell on a Friday. On which day of the week

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by GMATGuruNY » Wed Nov 21, 2018 6:35 pm
BTGmoderatorLU wrote:Source: GMAT Prep

June 25, 1982, fell on Friday. On which day of the week did June 25, 1987, fall? (Note: 1984 was a leap year)

A. Sunday
B. Monday
C. Tuesday
D. Wednesday
E. Thursday
Between 1982 and 1987 are 4 non-leap years and 1 leap year.
Each non-leap year is composed of 365 days; a leap year is composed of 366 days.
Thus, from June 25, 1982 to June 25, 1987, the total number of days = 4(365) + 366.

Since June 25, 1982 is a Friday, every passing of 7 days will yield another Friday.
364 is a multiple of 7.
Rephrase the total number of days in terms of 364:
4(365) + 366

= 4(364+1) + (364+2)

= (4*364 + 4) + (364+2)

= 5(364) + 6

= (multiple of 7) + 6

= Friday + 6 days

= Thursday.

The correct answer is E.
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BTGmoderatorLU wrote:
Wed Nov 21, 2018 2:17 pm
Source: GMAT Prep

June 25, 1982, fell on Friday. On which day of the week did June 25, 1987, fall? (Note: 1984 was a leap year)

A. Sunday
B. Monday
C. Tuesday
D. Wednesday
E. Thursday

The OA is E.
Solution:

Since June 25, 1987 is exactly 5 years after June 25, 1982, including the 1 extra leap day in 1984, 5 x 365 + 1 = 1826 days have elapsed between the two dates. Since 1826/7 = 260 R 6, we see that 260 weeks and 6 days have elapsed between the two dates. Since June 25, 1982, fell on a Friday and June 25, 1987 would be 6 days after Friday, then June 25, 1987 fell on a Thursday.

Answer: E

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