648 is 54% of ?
find the unknown value.

The answer to this problem is 349.92. assuming that 648 is 100 we can rewrite the problem like so: 648=100. now we have 2 equations 648=100% x=54% since the left and right sides have the same unit we can do something like so: 648/x=100%/54% now solve 648/x=100/54
(648/x)*x=(100/54)*x       - we multiply both sides of the equation by x
648=1.8518518518519*x       - we divide both sides of the equation by (1.8518518518519) to get x
648/1.8518518518519=x 
349.92=x 
x=349.92

She should use 12/3 to measure

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