If two resistors of resistances R1=(4±0.5)Ω R2=(16±0.5)Ω are connected in (i)series (ii) parallel; find the equivalent resistance in each case with limits of percentage error

R2=1.6+-0.5ohm

for series combination:

Rs=R1+R2

=4+16=20ohm

error=0.5+0.5=+-1ohm

% error=(+-1/20)x100=5%

hence Rs=20+-1ohm=20 ohm+- 5%