It is currently Sat Dec 03, 2016 9:56 pm

 All times are UTC

 Page 1 of 1 [ 4 posts ]
 Print view Previous topic | Next topic
Author Message
 Post subject: Is there a technique for this?Posted: Tue Nov 06, 2007 10:58 am
What is the smallest number which must be added to 368 to make it exactly divisible by 27?

Is it just a case of performing a long division and seeing how much needs to be added to the remainder to make it up to 27 or is there a cleverer way?

Top

 Post subject: Posted: Tue Nov 06, 2007 11:04 am

Joined: Mon Jun 18, 2007 2:32 pm
Posts: 6963
Location: East Kent
not sure if it's any quicker, but I've just multiplied 27 by 10...270, then added mutiples of 27.

270 +54 = 324 (not enough)

another 27 =351 (not enough)

another 27 = 378 (10 over) so you need to add 10

Top

 Post subject: Posted: Tue Nov 06, 2007 12:57 pm
I'd say division so you get 13 something = 368, so you do 14x 27 which gives you 378 so 10 is the number.

Top

 Post subject: Posted: Sat Nov 10, 2007 7:43 pm
Not sure if this is worth the typing time but this method seems to work. It's a bit long-winded but at least it saves long division - providing the divisor isn't prime. Problem is explaining it

Most kids looking at the above example should instantly spot that 27 is the product of 9 and 3 - i.e. instant factorisation! Using the factors in any order they divide by first one (say 9) and then divide the integer of their answer by the other. They multiply their second remainder by their first divisor, add their first remainder and deduct it from the original divisor. Their answer will be what they have to add to the given number to reach the next multiple of the original divisor.

Here goes!

368 / 9 = 40 [r8]
40 / 3 = 13 [r1]
1 x 9 = 9 + 8 = 17
27 - 17 = 10

Here's another:

What needs to be added to 482 to make it divisible by 24?

24 = 6 x 4

482 / 6 = 80 [r2]
80 / 4 = 20 [r0] (Aha!!)
0 x 6 = 0 + 2 = 2
24 - 2 = 22

Test: 482 + 22 = 504 / 24 = 21

or the other way ...

482 / 4 = 120 [r2]
120 / 6 = 20 [r0]
0 x 4 = 0 + 2 = 2
24 - 2 = 22

Yup, it works!

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