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tonychandra11
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What 2 digit number (which is a integer) is the product of 05 Jan 2006, 12:50
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What 2 digit number (which is a integer) is the product of its digits. I have worked this problem out but looking for other solutions.

The answer is 36.



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tonychandra11
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What 2 digit number (which is a integer) is the product of 05 Jan 2006, 13:25
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sorry problem worded wrongly

what 2 digit number is twice the product of its digits . Apologies
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duttsit
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What 2 digit number (which is a integer) is the product of 05 Jan 2006, 15:54
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tonychandra11
sorry problem worded wrongly

what 2 digit number is twice the product of its digits . Apologies
Show more


the algebric approach helps you narrow down but i guess the best approach to this one is number plugging:

if xy is the number:
10 x + y = 2xy
divide all by xy gives:
10/y + 1/x = 2

from this we know:
x,y cannot be 0
y is > 5

rest..i will plug numbers on test day :)
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mahesh004
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What 2 digit number (which is a integer) is the product of 06 Jan 2006, 05:25
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duttsit, although it is a good idea to put up an equation, dividing it by xy makes it complext
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believe2
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What 2 digit number (which is a integer) is the product of 06 Jan 2006, 19:18
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duttsit
tonychandra11
sorry problem worded wrongly

what 2 digit number is twice the product of its digits . Apologies

the algebric approach helps you narrow down but i guess the best approach to this one is number plugging:

if xy is the number:
10 x + y = 2xy
divide all by xy gives:
10/y + 1/x = 2

from this we know:
x,y cannot be 0
y is > 5

rest..i will plug numbers on test day :)
Show more


duttsit .. . I think I would take your approach one step ahead..
10x + y = 2xy
=> x= y/ (2y -10)

Now, you get 2 pieces of info from this eqn.
a) 2y - 10 > 0 or y >5
b) y > 2y -10 or y < 10

.....its simple now.
Just try out values 6,7,8,9 for y.
So the only solytion is 36 as noted above
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What 2 digit number (which is a integer) is the product of 07 Jan 2006, 15:29
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The way i got it is :
2 digit number=> xy
Now as per the stem 10x+y=2(x*y)
10x+y=2xy => y= (10x)/(2x-1)
Lets do plugin
x y
1 10(Not possible as no wont be 2 digit)
2 Non Integer
3 6
So 36
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eskay05
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What 2 digit number (which is a integer) is the product of 07 Jan 2006, 17:57
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Let x be the digit in ten's place and y be the digit in unit's place.
From question stem: 10x + y = 2xy
Therefore, x = y/2(y-5)
Since x and y are digits of a 2-digit number, x and y are positive integers.
So, y must be greater than 5 and also y must be even.

Try the first even number greater than 5 => 6
If y = 6, x = 3 --> 2-digit number = 36



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Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
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