zainabmustapha0 zainabmustapha0

25-10-2014
Mathematics

contestada

A number is such that its ten digit is twice its unit digit. Prove that the number itself must be seven times the sum of its digit

Respuesta :

konrad509 konrad509

25-10-2014

x - ten digit
y - unit digit

[tex]x=2y\\ 10x+y=7(x+y)\\\\ 10\cdot2y+y=7(2y+y)\\ 20y+y=14y+7y\\ 21y=21y \Rightarrow y\in \mathb{R}\Rightarrow x\in \mathb{R}[/tex]

So it's true.

Answer Link

Otras preguntas

A kamikaze is the name of a fierce storm. From what nation is this name derived? China Korea Taiwan Japan

A job is mostly a way to earn a living. agree or disagree

A town experiences a smaller earthquake several days after a large one. What has occurred

If the area of a park is exactly halfway between 2.4 and 2.5 acres what is the area of the park

5 sweets cost 30p altogether. How much do 7 sweets cost?

By 1900, Germany's steel production exceeded all other countries except?

A relay team of four people run 3 miles. If each person runs the same distance how many miles does each person run?

if x = 3 calculate the value of 2x squared

What is 7/3 as a mixed number

According to Dickinson, was Parliament justified imposing taxes on the colonies