Dado el número N = 4752a, averigua qué valor ha de tomar "a" para que: a) N sea divisible por tres. b) N sea divisible por cinco. c) N sea divisible por 15. d) Cuando se divida N por 7 dé de resto 5.

I will answer it in English:

a) We have te number N = 4752a

if we want to divide it by 3, then the addition of all the digits must be a multiple of 3.

Sum = 4 + 7 + 5 + 2 + a = 6 + 7 + 5 + a = 18 + a

and 18 is a multiple of 3, then we can have, a = 0, a = 3, a = 6, a= 9

b) A number is divisible by 5 if it ends on 5 or 0, so the possible values of a are 0 and 5.

c) we know that 15*3 = 45

then 15*3000= 45000

now we have:

4752a - 45000 = 252a

15*13 = 2520

then we have that a must be equal to zero, and:

15*(13 + 3000) =  47520

d) We want a number that when we divide it by 7, the surpass is 5.

a number is divisible by 7 if the difference between the number without the units and the double of the units is 0 or a multiple of 7.

in N = 4752x the unit is a, then we have:

D = 4752 - 2*x

now, let's choose a such we have a multiple of 7

we know that 5746 is a multiple of 7, so we can choose x= 3 and get:

D = 4752 - 2*3 =   5746  

So the number N = 47523 is a multiple of 7, and when we divide it by 7 we will have a surpass of 0.

Then when we divide N + 5 by 7, we will have a surpass of 7.

This is: N + 5 = 47528

This means that the actual value of a that we need is 8.

this story was prepared by jim

mccullaugh in los angeles and

al stewart in new york.

new york the colossal success of "top gun" appears to have dramatically altered madison avenue's

perception of corporate sponsorship

of home video projects.

the paramount home video re- lease, featuring a 60- second diet

pepsi spot, was by no means the

first prerecorded video to carry an advertiser's plug, but it was the

first major theatrical release to do so. in the aftermath of the title's

success, paramount is widely ex- pected to ink a similar deal for

"crocodile dundee" or "star trek

iv" or both.

corporate america's new attraccds push british

recording sales

to 19% gain

london fueled by the compact

disk boom, the value of u.k. manu- facturer shipments of recordings

rose 19% in the 12 -month period ended march 1987, according to the

british phonographic industry.

total value of u.k. shipments for

the period was $755 million for all

configurations. (all value figures

are based on an exchange rate of

$1.68 to the pound sterling.)

cd sales totaled 10.7 million units

worth $121.3 million- compared

with 3.7 million units worth $39.5

million in the prior 12 months -and

accounted for two -thirds of the

overall gain in trade value. at present growth rates, says the bpi, cd

sales for calendar 1987 will reach 20

(continued on page 79)

step-by-step explanation:

answer:

c 60% on edg