A+b=10, c+d=18, a+c=12, b+d= 16. find the value of A, B,C and D? ​

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If a+b=8, b+c=10 and c+a=12, what is the value of a+b+c?

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Patrick Ivers, former mathematics & English instructor

Answered June 26, 2018

If a+b=8, b+c=10 and c+a=12, what is the value of a+b+c?

The puzzle is solved by defining each variable in terms of another variable & a number & then making substitutions. Begin by taking each sum to define one of the variables in terms of the other. (Different combinations are available, but I’ll follow the a,b,c order.)

a+b=8 becomes a=8-b

b+c=10 becomes b=10-c

c+a=12 becomes c=12-a

Now subtract two of the equations that contain the same variable. I’ll pick two that contain an a: c+a =12 & a+b=8. Subtracting the latter from the former eliminates the “a”s, leaving c-b=4. Adding b to both sides to isolate c gives c=b+4. From above we can take b=10-c to substitute for b in c=b+4, giving us c=(10-c) + 4). Simplify the right side to c=14-c, add c to both sides, giving 2c=14, & then divide both sides by 2 to obtain c=7.

Replace the c in b=10-c with 7 to

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Paul K. Young, Former PhD candidate in Mathematics

Answered September 28, 2016

If A = B and B = C, does A = C?

In mathematics = is assumed to be a transitive relationship. Transitivity means precisely what you stated: A = B and B = C implies A = C.

While it’s possible to use = to represent a non-transitive relationship this would be considered an abuse of notation. A ~ B or R(A, B) would be a better way to express the relation in this case.

Similar assumptions are made about operators like + and *. + is generally assumed to be commutative, whereas * can be used for noncommutative operations like matrix multiplication. E.g. A * B != B * A.

Equality in programming is another story entirely.

In many languages = is the assignment operator and == is the equality operator. Assignment is not transitive - it’s not even a relation.There are cases where the equality operator doesn’t define a transitive relation.

option 1 is correct.

step-by-step explanation:

y varies inversely with x and constant of variation is 4

the equation will be:

y = k/x

where k =4 so,

y = 4/x

if we put values of x of option 1 in the above equation and find values of y

y = 4/-2 => y =-2

y = 4/-1 => y = -4

y = 4/1 => y = 4

y = 4/2 => y =2

so, all the values of x and y are correct.

if we put values of x given in other options and find value of y we cannot find whole table satisfying the equation.

hence option 1 is correct.