(a).Add `3.8 xx 10^(-6) to 4.2 xx 10^(-5)` with due regard to significant figures.
(b). Subtract `3.2 xx 10^(-6) from 4.7 xx 10^(-4)` with regard to significant figures.
( c ). Subtract `1.5 xx 10^(3) from 4.8 xx 10^(4)` with due regard to significant figures.

Answer

(a). `~ 4.6 xx 10^(-5)`; (b). `~ 4.7 xx 10^(-4)`; ( c ) `~ 4.6 xx 10^(4)`

Explanation

(a). `3.8 xx 10^(-6) + 4.2 xx 10^(-5) = 0.38 xx 10^(-5) + 4.2 xx 10^(-5)`
` = 4.58 xx 10^(-5) ~ 4.6 xx 10^(-5)`
[ up to one place of decimal]
(b). `4.7 xx 10^(-4) - 3.2 xx 10^(-6) = 4.7 xx 10^(-4) - 0.032 xx 10^(-4)`
`= 4.668 xx 10^(-4) ~ 4.7 xx 10^(-4)`
[ one decimal place]
( c ) `4.8 xx 10^(4) - 1.5 xx 10^(3) = 4.8 xx 10^(4) - 0.15 xx 10^(4)`
`= 4.65 xx 10^(4) ~ 4.6 xx 10^(4)`
[one decimal place]