It is currently Wed Dec 07, 2016 10:44 am

 All times are UTC

 Page 1 of 1 [ 4 posts ]
 Print view Previous topic | Next topic
Author Message
 Post subject: Maths HelpPosted: Mon Nov 05, 2007 8:39 pm
Two electric clocks with hours 1 to 12 marked on their faces.
The first clock gains 20mins per day and the second gains 15mins per day. They are both set to the correct time of 8o'clock.

1. After how many days has the first clock gained 12hrs?

2. After how many days has the second clock gained 12hrs?

3. When the second clock gained 12hrs it will be showing 8o'clock, what time will then be shown on the first clock?

4. After how many days (from start) will both clocks again be showing the same time?

Top

 Post subject: Posted: Wed Nov 07, 2007 12:51 pm

Joined: Wed Oct 31, 2007 3:15 pm
Posts: 78
Hi there guest27,
I think the answers are as follows:

1) The first clock gains 20mins per day, so it gains 1 hour every 3days.
Therefore it takes 3 x 12 days to gain 12 hours, so the answer is 36 days.

2) The second clock gains 15 mins per day, so it gains 1 hour every 4 days. Therefore it takes 4 x 12 days to gain 12 hours, so the answer is 48 days.

3) It takes 48 days for the second clock to gain 12 hours. So after 48 days the first clock will have gained 48 x 20 mins = 960 mins = 16 hours.
If it had gained 12 hours it would be 8 0'clock again so 4 more hours after this is 12 o'clock.

4) The first clock takes 36 days to gain 12 hours.
The second clock takes 48 days to gain 12 hours.
So we need to find the Lowest Common Multiple of 36 and 48.
You can do this either by working out the prime factors or by simply writing out the 36 and the 48 times tables. This gives:
36 - 36,72,108,144
48 - 48, 96,144

So the Lowest Common Multiple is 144, so the clocks would be showing the same time after 144 days.

abcdef

Top

 Post subject: Posted: Wed Nov 07, 2007 4:01 pm
Thank you so much..

Top

 Post subject: Posted: Wed Nov 07, 2007 10:07 pm

Joined: Fri Jul 06, 2007 8:31 pm
Posts: 1192
guest27 wrote:
Thank you so much..

That is a hard question. (Or the last part at least).

Where did it come from?

Regards
SVE

_________________
Animis opibusque parati

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 4 posts ]

 All times are UTC

#### Who is online

Users browsing this forum: No registered users and 1 guest

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

Search for:
 Jump to:  Select a forum ------------------ FORUM RULES    Forum Rules and FAQs 11 PLUS SUBJECTS    VERBAL REASONING    MATHS    ENGLISH    NON-VERBAL REASONING    CEM 11 Plus GENERAL    GENERAL 11 PLUS TOPICS    11 PLUS APPEALS    11 PLUS TUTORS    INDEPENDENT SCHOOLS    11 PLUS CDs/SOFTWARE    11 PLUS TIPS    PRIMARY    SEN and the 11 PLUS    EVERYTHING ELSE .... 11 PLUS REGIONS    Berkshire    Bexley and Bromley    Birmingham, Walsall, Wolverhampton and Wrekin    Buckinghamshire    Devon    Dorset    Essex    Essex - Redbridge    Gloucestershire    Hertfordshire (South West)    Hertfordshire (Other and North London)    Kent    Lancashire & Cumbria    Lincolnshire    Medway    Northern Ireland    Surrey (Sutton, Kingston and Wandsworth)    Trafford    Warwickshire    Wiltshire    Wirral    Yorkshire BEYOND 11 PLUS    Beyond 11 Plus - General    GCSEs    6th Form    University