Young's modulus is a quantitative measure of stiffness of an elastic material. suppose that for aluminum alloy sheets of a particular type, its mean value and standard deviation are 70 gpa and 1.6 gpa, respectively (values given in the article "influence of material properties variability on springback and thinning in sheet stamping processes: a stochastic analysis" (intl. j. of advanced manuf. tech., 2010: 117–

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.

D- dialation and reflection