Apply logic part 4

Find the total number of digits in the number 2 2005 × 5 2000 { 2 }^{ 2005 }\times { 5 }^{ 2000 } , when it is multiplied out.

100002 2 4005 { 2 }^{ 4005 } 2 2005 { 2 }^{ 2005 } 2002 10

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10 solutions

2 2005 × 5 2000 = 2 5 . 2 2000 . 5 2000 = 2 5 ( 2.5 ) 2000 = 32. 10 2000 n o w , 10 2000 c o n t a i n s 2000 z e r o e s a f t e r 1 a n d , 32. 10 2000 = 32 f o l l o w e d b y 2000 z e r o e s . T o t a l n o . o f d i g i t s = ( 2000 + 2 ) = 2002 { 2 }^{ 2005 }\times { 5 }^{ 2000 }={ 2 }^{ 5 }.{ 2 }^{ 2000 }.{ 5 }^{ 2000 }\\ \quad \quad \quad \quad \quad \quad \quad \quad ={ 2 }^{ 5 }{ \left( 2.5 \right) }^{ 2000 }\\ \quad \quad \quad \quad \quad \quad \quad \quad =32.{ 10 }^{ 2000 }\quad \quad \\ now,\quad \\ { 10 }^{ 2000 }\quad contains\quad 2000\quad zeroes\quad after\quad 1\\ and,\quad \quad 32.{ 10 }^{ 2000 }=32\quad followed\quad by\quad 2000\quad zeroes.\\ \therefore \quad Total\quad no.\quad of\quad digits=(2000+2)=2002

i did same

Dev Sharma - 5 years, 9 months ago

How does 32 (2.5)^2000=32 (10)^2000?

Adam Garland - 5 years, 9 months ago

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The dots are meant for multiplication, they aren't decimal points.

Dinesh Nath Goswami - 5 years, 9 months ago

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The L a T e X LaTeX command for a multiplication dot is \cdot.

Hobart Pao - 5 years, 9 months ago

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@Hobart Pao I believe it's \times × \times

Ahmed Obaiedallah - 5 years, 8 months ago

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@Ahmed Obaiedallah either one, depending if you want a dot or a cross.

Hobart Pao - 5 years, 8 months ago
Michael Fuller
Sep 1, 2015

2 2005 × 5 2000 = 2 5 × 2 2000 × 5 2000 = 2 5 × 10 2000 = 32 × 100000 0 2000 z e r o e s = 3200000 0 2000 z e r o e s \large{{ 2 }^{ 2005 }\times { 5 }^{ 2000 }\\ ={ { 2 }^{ 5 }\times 2 }^{ 2000 }\times { 5 }^{ 2000 }\\ ={ 2 }^{ 5 }\times { 10 }^{ 2000 }\\ =32\times \underbrace { 100000\dots 0 }_{ 2000\quad zeroes } \\ =\underbrace { 3200000\dots 0 }_{ 2000\quad zeroes } }

Therefore the total number of digits is 2002 \large \color{#20A900}{\boxed{2002}} .

Rewrite the given expression: 2 2000 × 2 5 × 5 2000 2^{2000} \times 2^5 \times 5^{2000} = 1 0 2000 × 32 10^{2000} \times 32 . The number 1 0 2000 10^{2000} has 2000 zeros, and 1 × 32 1 \times 32 has 2 digits. In total there are 2000 + 2 = 2002 digits.

. .
Jan 2, 2021

2 2005 × 5 2000 = 2 2000 × 5 2000 × 2 5 = 1 0 2000 × 2 5 = 2000 + 2 = 2002 2^{2005} \times 5^{2000} = 2^{2000} \times 5^{2000} \times 2^{5} = 10^{2000} \times 2^{5} = 2000+2=2002

Tootie Frootie
Sep 5, 2015

2^5 × 2^2000 × 5^2000 = 32 × 10^2000 = 3.2 × 10^2001, so 2002 digits.

Shawn Pereira
Sep 5, 2015

2 2005 5 2000 = 2 2000 + 5 5 2000 { 2 }^{ 2005 }{ 5 }^{ 2000 }=\quad 2^{ 2000+5 }5^{ 2000 }

= 2 5 ( 2 2000 5 2000 ) =\quad { 2 }^{ 5 }(2^{ 2000 }5^{ 2000 })

= 2 5 ( 2 5 ) 2000 = 2 5 ( 10 ) 2000 = 32 10 2000 =\quad { 2 }^{ 5 }(2*5)^{ 2000 }=\quad { 2 }^{ 5 }(10)^{ 2000 }=32*{10}^{2000}

We know that 10 2000 {10}^{2000} contains 2000 zeros + one 1. Therefore it contains 2001 digits. However, when 32 is multiplied to 10 2000 {10}^{2000} we get 32 followed by 2000 zeroes; so 2+2000 digits. Therefore, the number contains 2002 digits.

Hadia Qadir
Sep 1, 2015

2^2005 x 5^2000 = 2^5 x 2^2000 x 5^2000 = 32 x (2 x 5)^2000 = 32 x 10^2000 Therefore, the answer has 2 + 2000 = 2002 digits.

Atika Samiha
Sep 1, 2015

((2^2000)x(5^2000))x2^5 =10^2000x32 so, we have total (2000+2) digits in total. here,2 is for 32&1

Samir Mohamed
Sep 1, 2015

2^1 * 5^1 = 10 then 2 digits

2^3 * 5^3 = 1000 then 4 digits

so, num of digits = power + 1

2^2000 * 5^2000 then 2001 digits => 2000 zeros & 1 one

and , 2^5 = 32

when 32 * 1 , num of digits increase by 1

so the result is 2002 digits

Aaysha Babu
Aug 29, 2015

2^2005 5^2000 =2^5 (2 5)^2000 =32 10^2000 since 10^2000 has 2000 zeroes followed by one 10^2000*32 has2002 digits

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