Question

Sum of H.C.F. and L.C.M. of $4,20$ and $28$ is

• A. $140$
• B. $144$
• C. $74$
• D. $81$

Answer 1

The correct option is B $144$

HCF of $4,20,28$

$2|4,20,28$

______________

$2|2,10,14$

______________

$5|1,5,7$

______________

$7|1,1,7$

______________

$1,1,2$

$\therefore$LCM$=2\times 2\times 5\times 7=2^2\times 5\times 7$

HCF$=2^2$

Sum of LCM$+$HCF

$=2\times 2\times 5\times 7\times 4=140+4$

$=144$.