Decimals

tenths digit is the first digit to the right of the decimal point.

Similar Triangles

Triangles are defined as similar if all their corresponding angles are equal or if the lengths of their corresponding sides have the same ratios.

First, recall that in a right triangle, the two shorter sides intersect at the right angle.

if two similar figures have lengths in a given ratio (say A:B), then their areas will have a ratio that is the square of this length ratio (i.e.,A²:B²). Conversely, if the areas are in a given ratio, then the lengths will be in the square root of that ratio. ( Look at MGMAT CAT 4. q 19) Excellent example.

Mean & Standard Deviation

1) If we multiply each element of a set by a common factor/ (or increase/decrease each element by fixed %) / ( increase/decrease each element by the same amount then):

New Mean or New SD = Old Mean or Old SD * common factor.

New Mean or New SD = Old Mean or old SD * (1+% increase/decrease)

New Mean or New SD = Old Mean or Old SD + increase/decrease in amount.