Answer:

(a). ~4.6×10−5; (b). ~4.7×10−4; ( c ) ~4.6×104

Step-by-step explanation:

(a). 3.8×10−6+4.2×10−5=0.38×10−5+4.2×10−5

=4.58×10−5~4.6×10−5

[ up to one place of decimal]

(b). 4.7×10−4−3.2×10−6=4.7×10−4−0.032×10−4

=4.668×10−4~4.7×10−4

[ one decimal place]

( c ) 4.8×104−1.5×103=4.8×104−0.15×104

=4.65×104~4.6×104

[one decimal place]