math test , if 9 = 90 , 8 = 72 , 7 = 56 , 6 = 42 , 3 = ?

[johnwagnon]

Each line cannot be independent of the other. In the absence of operator, one must assume + between lines.

[mrsubirroy]

This explanation is INCORRECT, series 6 & 3 are continuous, so there must be dotted lines for continuous indication, so answer must be 18 not 12.

[a-pfhx]

9 = 90
8 = 72
7 = 56
6 = 42
3 = ?

90/9 = 10
72/8 = 9
56/7 = 8
42/6 = 7

So, a pattern can be observed.
Since 9 = 90.
Let 9 be (L) for left and 90 be (R) for right.
We can say that the ratio of R/L = C,
In which case C = L+1.

Therefore, we can use the following relations. Which are:
R/L = C and C = L+1

To deduce the relation that:
R/L = L+1
Since we need to find R, we multiply by L on both sides:
R = L^2 + L

Upon substitution, we get that:
R = 3^2 + 3
R = 12

So, 3 = 12.

[Menalix]

The answer is 12, if you think logical, as the rule of thumb is we must reverse the calculation to a function which the result derived from, that function would be: f(x)= x(x+1)

[navinator]

This question is flawed because there is equal spacing between 9, 8, 7, 6, but then the numbers jump to 3 without having the blank spacing included for 5, and 4.
To answer your questions,
5= 30
4 = 20
3 = 12

[isaytheenay]

3=3.
The formula is a pattern of error. X=X(X+1). This can only be true when X = 0. Because "0=" is not given, In every single line, it's false.
3 always = some expression of 3. Under no condition can it EVER equal 12 or 18.
All other answers are absolutely, definitely, false. Provably false.
There is a lesson in human nature here. When taught repeated error, our tendency is to output yet more error.

[teacherjn]

Solution:
Let n be any number
Pattern is: n x (n+1)

9 = 9 x (9+1) = 90
8 = 8 x (8+1) = 72
7 = 7 x (7+1) = 56
6 = 6 x (6+1) = 42
3 = 3 x (3+1) = 12

answer: 12

[vinoddodhia]

I agree that there may be more than one pattern. But the pattern that yields the answer 18 is not fully supported based on how the puzzle is presented.



If the puzzle was presented as: 100 = ?, 9 = 90, 8 = 72, 7 = 56, 6 = 42, 3 = ?
What would the answers be for 100 = ? and 3 = ?

With N*(N+1) pattern


I can easily say 100 = 10100 and 3 = 12.
And according to alternate pattern some people are suggesting here, 9 = 90 would be incorrect.

[itsameme]

the answer may also be 36, If u subtract the numbers consecutively then u may observe that their difference is decreasing by 2 and if u find it for 3 u will get 36

[NicoDurand]

There are really 2 ways to look at this: n*(n+1), or n*theNumberAbove.
Both are absolutely right IMHO, but the second one is slightly more correct.
It all depends if you need to guess the formula, or complete the series. Here, it's clearly a series test, so ?=18.

[stuartmackay]

There are at least 3 ways of coming up with 12, decreasing subtraction, decreasing multiplication. So, 12 if you like, all results are coincident if you add the missing lines…

just to be different?? we'll see, let’s say:



9 tubs of sweets have 90

8 tubs should have 80, but because we have decreased 9 to 8 in 1 step (80-(8x1)) = 72

7 (70-(7x2)) = 56

6 (60-(6x3)) = 42

3 (30-(3x4)) = 18

Where did all the sweets go someone ate them of course



As said, we could consolidate the first three methods to get to 12 by inserting another two lines can this also be consolidated in the same manner?



6 (60-(6x3)) = 42

5 (50-(5x4)) = 30

4 (40-(4x5)) = 20

3 (30-(3x6)) = 12 … 3 being a third of 9 … 30 being a third of 90



So again; 4 ways of showing 12 is a likely candidate if we assume there are missing lines…



Now let’s say the equal sign is an operator for an unknown sequence not either side of an equation:



Say 990 (== operator) reduction by an ever-decreasing amount 990 – 872 = written after what we now as the hundred columns indicating the operator is in the 100 values above 99, and before the thousand digits indicating it is below 1000 operator -100 to -999 range.



9 = 90 – 118

8 = 72 -116

7 = 56 - 114

6 = 42 - 112

5 = 30 - 110

4 = 20 - 108

3 = 12 again



Or 9 - -90; 8 - -72… decreasing difference in numbers



9 = 90 (99 – 19)

8 = 72 (80 – 17)

7 = 56 (63 – 15)

6 = 42 (48 – 13)

5 = 30 (35 -11)

4 = 20 (24 – 9)

3 = (12) 15 again 12, , ,



or lets say we can only use the left hand number and (arithmetic operators) to come up with a relative sequence:



9 = 90 9x9+9

8 = 72 8x8+8

7 = 56 7x7+7

6 = 42 6x6+6

3 = 12 3x3+3 no surprise 12



what if we didn't want 12 or 18 to be the answer?



Primary school kids are given some cards marked with various numbers 1-20 each card has a quantity written on it 90; 72; 56; 300; 200, 30, 12 and so forth, the kids are asked to find a maths sequence and put the numbered card that fits the sequence, so card 3 will have 30 written on it!



The 9, 8, 7, 6 were just a chance occurrence for the 90 (-18) starting point, no missing lines, no use of multiple maths operators or guessing numbers X*(x+1)…



9 = 90

8 = 72 (-18)

7 = 56 (-16)

6 = 42 (-14)

3 = 30 (-12)

[scrapplepig]

The answer is 18 You have no right to assume that there are supposed to be anymore numbers than the ones pictured.

[kephryccephryc]

the problem with this is becuz its jsut X = X since it looks like it just bunch of 9 +81 = 90 8 + 64 =72 and not a 3x4 =12 9x10 thers just no iffo in this if its + = or x = math

[SATYAPRAKASH-dbjj]

Jaise 9×9+9=90
8×8+8=72
7×7+7=56
6×6+6=42
Waise hi 3×3+3=12 ✓ hoga ok 👍👍

[totallynothatguy]

Why is everyone acting big brain? The answer isn't very hard to get, nor is it very mathematical.

[courtneyannvd]

I got 18 that 12 making no sense to me 😭😂

[tarshabell]

I would say that the answer is 6
9*8=72-16=56
8*7=56-14=42
7*6=42-12=30
6*5=30-10=20
5*4=20-8=12
4*3=12-6=6
3*2=6

[kudretyslbs]

A = (a x10) - (0 x a )

A = (a x10) - (1 x a)

A = (a x10) - (2 x a)

A= (a x10) - (3 x a)

A = (a x10) - (4 x a).

Ans : 18

[bayozan]

Oppo Reno 4 incelemesine geldim sandım başta. Burda da mı Hintli yaw.

[SHASHANKVERMAHR]

Answer is wrong. Righy Answer is 6. First comment