Question

d * 7 = mod 120
How to calculate the value of d?

Answer 1

do you mean :
\[\large d*7 \equiv 0 \mod 120\]

?

Answer 2

No. The question is typed correctly. And I don't think it is =0

Answer 3

the question appears to me like asking to calculate `7x dividied by` without specifing what one wants to divide by

Answer 4

Exactly. Anyways,how would you solve if the problem was d∗7≡0mod120

Answer 5

its called linear congruence, there is a standard way to solve congruences of type :

\[\large ax \equiv b \mod n\]

Answer 6

for your problem \(d*7 \equiv 0 \mod n\), the answer is \(\large d = 0\)

Answer 7

But in general, we can solve these by converting it into a diophantine equation :

\[\large ax-ny = b\]

Answer 8

familiar with solving a linear diophantine equation ?

Answer 9

What could be the value of d if problem was d∗7≡1 mod120

Answer 10

that looks like a more correct question :)

Answer 11

basically you're trying to find the multiplicative invese of 7 in mod 120

Answer 12

\[\large d*7 \equiv 1 \mod 120\]

Answer 13

the answer is \(\large d = 103\) cuz 103*7 -1 is divisible by 120

Answer 14

want to see how to work it ? :)

Answer 15

no thanks I get it

Answer 16

Actually I wasn't sure myself if the question was correct in its original form. The correct question is as you said d∗7≡1mod120. Thanks for your time.

Answer 17

np :)