Three-sevenths of a number is 21. find the number.

the number is 9
the number is 27
the number is 49

Step-by-step explanation:

The number is 49, First do 21 / 3 to find what 1/7 of the number is. We get 7, so we know 1/7 is 7 so if we do 7 x 7 we will have 7/7 or one whole and 7x7 is 49. Hope this helps

The number is 49

Step-by-step explanation:

Let the number be x

From the question,  of   x   =   21

                                  × x  = 21

                                  = 21

Multiply both-side of the equation by 7

                                    × 7 = 21 × 7

(On the left-hand side of the equation, 7 at the numerator will cancel-out 7 at the denominator leaving us with just 3x)

                                      3x  = 147

Divide both-side of the equation by 3

                                        =  

(On the left-hand side of the equation 3 at the numerator will cancel-out 3 at the denominator, while on the right-hand side of the equation 147 will be divided by 3)

                            x  =

                              x=49

Therefore the number is 49

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents