perplexus.info :: Just Math : What´s the trick?

What´s the trick? (Posted on 2005-08-25)

I give you 6 cubes with 3-digit numbers in their faces:

cube 1: 643 / 445 / 742 / 247 / 346 / 544
cube 2: 465 / 564 / 267 / 366 / 762 / 663
cube 3: 186 / 285 / 384 / 483 / 681 / 582
cube 4: 821 / 227 / 722 / 623 / 326 / 128
cube 5: 533 / 137 / 236 / 335 / 632 / 731
cube 6: 278 / 377 / 179 / 872 / 773 / 971

I bet you that every time you throw them, I can evaluate (mentally) the sum of the 6 three-digit numbers that appear in the top faces faster than you, even if you use a calculator (about 6 or 7 seconds, and I´m not too good at mental calculations).

Explain how I can do this.

Submitted by pcbouhid

Rating: 2.8000 (5 votes)

Solution: (Hide)

All I have to do is sum the unit digits of all the 6 cubes, subtract the total from 55 (always 55), and juxtapose the two numbers so obtained.

Example: if the sum of the unit digits is 26 (what I can do in few seconds), 55 - 26 = 29, and the total is 2,926.

I leave to you explain why this always works.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
re: the sum is always a constant=82	pcbouhid	2005-08-31 12:29:35
the sum is always a constant=82	thanveer	2005-08-31 09:31:36
re: Hmm, am I misreading this? To you and to pratik...	pcbouhid	2005-08-29 01:17:57
Hmm, am I misreading this?	Matt	2005-08-29 01:03:47
Good one...	pratik	2005-08-29 00:30:06
Solution	Thomas Harris	2005-08-27 19:33:18
re: i know	pcbouhid	2005-08-27 03:10:59
i know	Nicole	2005-08-26 22:56:18
Clarification	Ken Haley	2005-08-26 05:48:03
re: No Subject	nickson	2005-08-26 03:26:47
re(2): ss-t!	sragen	2005-08-26 03:23:29
No Subject	Will	2005-08-25 19:04:36
re: ss-t!	nickson	2005-08-25 10:46:19
ss-t!	sragen	2005-08-25 06:58:51

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