Which cancellation should I use?

( 2015 ! + 2016 ! 2015 ! × 2016 ! ) × 2016 ! = ? \large \left( \frac { 2015!+2016! }{ 2015!\times 2016! } \right) \times 2016! = \ ?


The answer is 2017.

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23 solutions

Sharky Kesa
Apr 25, 2015

( 2015 ! + 2016 ! 2015 ! 2016 ! ) 2016 ! = 2015 ! + 2016 ! 2015 ! = 1 + 2016 ! 2015 ! = 1 + 2016 = 2017 \begin{aligned} \left (\dfrac {2015! + 2016!}{2015! \cdot 2016!} \right) \cdot 2016! & = \dfrac {2015!+2016!}{2015!} \\ & = 1 + \dfrac {2016!}{2015!}\\ & = 1 + 2016\\ & = 2017 \end{aligned}

Moderator note:

Simple! I was thinking of A + B A B = 1 A + 1 B \frac {A+B}{AB} = \frac 1A + \frac 1 B .

Better solution than that of others. 👍

siddharth bhatt - 6 years, 1 month ago

wouldn't it be like: (2015!+2016!)*2016!


2015!*2016!

2015!+2016!


2015!

2015! + 2016! __ 2015! 2015!

1 + 2016 ------ 2015

!+1.0004

2.0004

Humza Riaz - 5 years, 8 months ago
Nihar Mahajan
Apr 25, 2015

Let 2015 ! = a , 2016 ! = 2016 a 2015! = a , 2016! = 2016a

So the expression becomes: a + 2016 a 2016 a 2 × 2016 a = 2017 a a = 2017 \dfrac{a+2016a}{2016a^2} \times 2016a =\dfrac{2017a}{a} = \huge\boxed{2017}

Moderator note:

Nicely done.

Ubaidullah Khan
Apr 28, 2015

emm, i want to know why we must to (+1) at the 4th step?

Beta 27 - 6 years, 1 month ago

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he took 2015 ! 2015! common as

2016 ! = 2015 ! × 2016 2016!=2015!\times2016

so

2015 ! × 1 + 2015 ! × 2016 = 2015 ! × ( 1 + 2016 ) 2015!\times1+2015!\times2016=2015!\times(1+2016)

Ahmed Obaiedallah - 5 years, 11 months ago

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oohh... ic... thanks

Beta 27 - 5 years, 11 months ago

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@Beta 27 You're welcome

Ahmed Obaiedallah - 5 years, 11 months ago

This is the way I did it :)

Stephanie Ringgold - 5 years, 8 months ago
Kyle Finch
Apr 25, 2015

2015 ! × 2017 × 2016 ! 2015 ! × 2016 ! \frac{2015!\times 2017\times 2016!}{2015!\times 2016!}

=2017

Moderator note:

Can you solve this without factoring out 2017 2017 from 2015 ! + 2016 ! 2015! + 2016! ?

Leonard Zuniga
Apr 29, 2015

2015 ! + 2016 ! 2015 ! 2016 ! 2016 ! \frac{2015! + 2016!}{2015! 2016!} 2016!

Simplify by multiplying 2016 ! 2016! and 1 2016 ! \frac{1}{2016!} , cancelling each other. The new equation would look like this: 2015 ! + 2016 ! 2015 ! \frac{2015! + 2016!}{2015!} Factoring 2015 ! 2015! from the numerator would give: 2015 ! ( 1 + 2016 ) 2015 ! \frac{2015! \left( 1 + 2016 \right)}{2015!} Simplifying, we'll get 1 + 2016 = 2017 1 + 2016 = \boxed{2017}

Christian Daang
Apr 28, 2015

Solution:

2015 ! + 2016 ! 2015 ! 2016 ! 2016 ! \dfrac{2015! + 2016!}{2015! * 2016!} * 2016! = 2015 ! + 2016 ! 2015 ! \dfrac{2015! + 2016!}{2015!} = 2015 ! 2015 ! + 2016 ! 2015 ! \dfrac{2015!}{2015!} + \dfrac{2016!}{2015!} = 1 + 2016 1 + 2016 = 2017 \boxed{2017}

Ramez Hindi
Apr 28, 2015

First look at 2015 ! + 2016 ! = 2015 ! + 2016 × 2015 ! = 2015 ! ( 1 + 2016 ) = 2017 × 2015 ! 2015!+2016!=2015!+2016\times 2015!=2015!(1+2016)=2017\times 2015!

so 2015 ! + 2016 ! 2015 ! × 2016 ! × 2016 ! = 2017 × 2015 ! 2015 ! × 2016 × 2016 ! = 2017 \frac{2015!+2016!}{2015!\times2016!}\times 2016! =\frac{2017\times2015!}{2015!\times2016}\times2016!=2017

Aravind Amuthuraj
Apr 28, 2015

((2015!+2016!)/(2015!.2016!)).2016!=((2015!+2016!)/2015!) =1+(2016!/2015!)=1+(2016.2015!/2015!)=1+2016=2017

Suresh Kumar
Apr 27, 2015

(2015!(1+2016))/(2015!.2016!)*2016!=2017

Kevin Silva
Apr 27, 2015

( (2015 ! +2016 ! )/2015 ! * 2016 ! )(2016 ! )

(2015 ! (1+2016)/2015 ! * 2016!)(2016 ! )

(2015 !) (2017)/2015 !

2017

Betty BellaItalia
Dec 18, 2017

The 2016! in the denominator and the 2016! outside the fraction will cancel off, leaving you (2015!+2016!)/2015!. You can treat the new fraction as (2015!/2015!)+(2016!/2015!). The first fraction tends to 1, while 2016! can be expressed as 2016x2015!, making the second fraction (2016x2015!)/2015!. Another cancellation will give you 2016. Adding 1 and 2016 will give you 2017.

Alex Badalyan
Sep 22, 2015

(2015! (1+2016)/2015!.2016!) 2016!=(2015!.2017/2015!.2016!) 2016!= 2017

Hadia Qadir
Sep 22, 2015

The given questions Turns into 2015!/2015!+2016!/2015! =1+2016!/2015! =1+2016 =2017

Amad Shahzad
Sep 22, 2015

Let 2!=2015! & 3!=2016! By solving it I got the answer 4..It means that whenever you try to solve two consecutive numbers you will get the next number Therefore my answer is 2017

Jake Globio
Sep 22, 2015

= 2015!/2015! + 2016 × 2015!/2015! = 1 + 2016 = 2017

Atika Samiha
Sep 22, 2015

((2015)!x(2016+1))/(2015!x2016!)x 2016! 2017

Talha Bin Adam
May 13, 2015

[(2015! + 2016!) ÷ (2015! × 2016!)] × 2016!

= (2015! + 2016!) ÷ 2015!

= 1 + (2016! ÷ 2015!)

= 1 + 2016 ☞(n + 1)! ÷ n! = n+1

= 2017

Raju Pratama
May 13, 2015

( 2015 ! + 2016 ! 2015 ! 2016 ! ) 2016 ! = 2015 ! + 2016 ! 2015 ! = 1 + 2016 = 2017 \begin{aligned}\left(\dfrac {2015! + 2016!}{2015! \cdot 2016!}\right) \cdot 2016! & = \dfrac {2015! + 2016!}{2015!}\\ & = 1 + 2016\\ & = 2017 \end{aligned}

Jia Butt
May 3, 2015

(2015!+2015!.2016)/2015! 2015!(1+2016)/2015! (1+2016)=2017

Chinmayee Behera
Apr 30, 2015

(2015!(1+2016))/(2015! 2016!) 2016! =2017/2016!*2016! =2017

Diego G.M
Apr 29, 2015

Note that if we divide every term of the numerator and denominator by 2016!, we obtain 2017. Proof: Let 2015!=a , 2016!=b be. Then ([(a/b) + (b/b)] (b/b))/((a/b) (b/b)). Now we must know that a/b=1/2016 and b/b=1. If we calcule it, we'll obtain 2017.

Hobart Pao
Apr 28, 2015

Mental math. Factored numerator and canceled 2015! and 2016! which leaves 2017

Are u mental?

Pratik Dhanuka - 5 years, 1 month ago

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Please don't start fights on brilliant.

Hobart Pao - 5 years, 1 month ago

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