GMAT Prep Arithmetic Sequence??

[dferm]

Please Help to Understand...

[Neo2000]

Simple Equations!!

We know that 7X +77Y = 350 and they want you to find X+Y
Or X +11Y = 50

If Y = 1, X = 39 Right here, you realise this is present in the answer options.
if Y = 2, X = 28 The sum of X&Y is less than answer options. Stop here!!

[dalwow]

Another way to answer this is...

350 - 77 = 273

273/7 = 39

39 + 1 (which is for the one 77 term we have) = 40

[codesnooker]

Simple Equations!!

We know that 7X +77Y = 350 and they want you to find X+Y
Or X +11Y = 50

If Y = 1, X = 39 Right here, you realise this is present in the answer options.
if Y = 2, X = 28 The sum of X&Y is less than answer options. Stop here!!

I guess, everyone here missing one important check.

in X + 11Y = 50, X can be ZERO also.

Fortunately 50 is not present in the choices. (However, in real GMAT, you would not find ambiguous answers).

But point to note that, you must always check the equation with ZERO rather than ONE.

[Neo2000]

I guess, everyone here missing one important check.
in X + 11Y = 50, X can be ZERO also.
Fortunately 50 is not present in the choices. (However, in real GMAT, you would not find ambiguous answers).
But point to note that, you must always check the equation with ZERO rather than ONE.

If X = 0 then 11Y = 50 what value would Y take for an ODDxEven = Even?

I believe you are asking what if Y = 0? Fair enough but in that case it would mean there are no 77 which according to the question is not possible. There has to be atleast 1 77

[codesnooker]

Nope I never asked what is the value of Y when X = 0. I guess I know simple calculation.

Secondly, if we read question again, it said that the terms present in the equation is either 7 or 77. It doesn't mean that there must be at least one term which must be 77 or 7. It can be all 7s or all 77s. No offense, but the question is stated in simple English.

The whole idea of my post is to remember that in such cases, we must check the equation with keeping either of the variable = 0. If there is no matching answer, then only should proceed further.

So yes, if instead of 39, if 50 was not present in the choices, then we have chosen 50.

In software technology, this kind of the test is called as "Boundary Value Testing". That to check the condition at Boundary first rather any intermediate values. As most of the errors/problems occurred at boundaries.

The idea is just to share the knowledge and not to offend anyone. I hope you take my point in right spirit. Sorry in case, if I hurt you by any means.