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Manager
Joined: 10 Dec 2020
Posts: 50
Given Kudos: 955
GRE 1: Q166 V162
Every hour, a clock chimes a number of times equal to the number of
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29 Nov 2021, 07:34
29 Nov 2021, 07:34
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Question Stats:
66% (01:35) correct
33% (01:40) wrong based on 6 sessions
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Every hour, a clock chimes a number of times equal to the number of the hour (for instance, at 6:00 pm, the clock chimes 6 times). How many times will the clock chime, in total, between 8:30 pm on Wednesday and 4:15 am on Friday of the same week?
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208
Manager
Joined: 10 Dec 2020
Posts: 50
Given Kudos: 955
GRE 1: Q166 V162
Re: Every hour, a clock chimes a number of times equal to the number of
[#permalink]
29 Nov 2021, 07:39
29 Nov 2021, 07:39
1
Official explanation from MGRE:
-- From 8:30pm to 12 midnight on Wednesday evening, the clock will chime 9 times (at 9:00 pm), then 10 times, then 11 times, then 12 times, for a total of 42 chimes.
-- During the first half of the day on Thursday, the clock will chime 1 + 2 + 3 + … + 12 times, from 1 am to 12 noon. Then, from 1 pm to 12 midnight, the clock again will chime 1 + 2 + 3 + … + 12 times. To save time, use the consecutive integer formula to calculate the sum of the numbers from 1 to 12 -----> 12 * [(1+12) / 2] = 78 chimes
-- Each time the clock goes through the hours from 1 o’clock to 12 o’clock, inclusive, it will chime 78 chimes.
-- Finally, the clock will chime 1 + 2 + 3 + 4 = 10 times from 1 am to 4 am on Friday.
Use the on-screen calculator to sum the four numbers in the table: 42 + 78 + 78 + 10 = 208 chimes.
The correct answer is 208.
-- From 8:30pm to 12 midnight on Wednesday evening, the clock will chime 9 times (at 9:00 pm), then 10 times, then 11 times, then 12 times, for a total of 42 chimes.
-- During the first half of the day on Thursday, the clock will chime 1 + 2 + 3 + … + 12 times, from 1 am to 12 noon. Then, from 1 pm to 12 midnight, the clock again will chime 1 + 2 + 3 + … + 12 times. To save time, use the consecutive integer formula to calculate the sum of the numbers from 1 to 12 -----> 12 * [(1+12) / 2] = 78 chimes
-- Each time the clock goes through the hours from 1 o’clock to 12 o’clock, inclusive, it will chime 78 chimes.
-- Finally, the clock will chime 1 + 2 + 3 + 4 = 10 times from 1 am to 4 am on Friday.
Use the on-screen calculator to sum the four numbers in the table: 42 + 78 + 78 + 10 = 208 chimes.
The correct answer is 208.
gmatclubot
Re: Every hour, a clock chimes a number of times equal to the number of [#permalink]
29 Nov 2021, 07:39
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