NUMBERS IN MEASUREMENTS

$19.$ Perform each calculation below and round each answer to the significant figures indicated in parentheses:

a$.75+77(2sf{)}_{-}$

b$.(284)(2sf)$

c$.5204(1sf)$

d$.455(2sf)$

e$.\frac{1}{3}(4sf)$

f$.\frac{16}{5}(1sf$

$20.$ Carry out the following multiplications using correctly written scientific notations. Answers must be given in correct significant figures and scientific notation:

a$.(3\mathrm{.}58{10}^{-6})(14\mathrm{.}24{10}^{15})$

b$.(2\mathrm{.}984{10}^7)(1\mathrm{.}1{10}^4)$

c$.(42\mathrm{.}55{10}^{-6})(9\mathrm{.}545{10}^{-15})$

d$.(11\mathrm{.}29{10}^5)(16\mathrm{.}98{10}^5)$

e$.(7\mathrm{.}75{10}^{-4})(8\mathrm{.}10{10}^4)$

f$.(4\mathrm{.}53{10}^{-6})(2\mathrm{.}333{10}^{15})$