Question

when we get 1/14. +. 1/30 .then what to do cross multiplication or what

Answer 1

here is no use of cross multiplication
in addition cross multiplication doesn't work
for multiplication this is a process

Answer 2

When we get

1/14 + 1/ 30 then

Find LCM of 14 & 30.

To find LCM factorise 14 & 30.

14 = 2×7
30 = 2×3×5

Now multiply all number with common factor i.e,

LCM = 2×7×3×5 = 210

Here LCM of 14 & 30 is 210.

Now, multiply the numerator with same number from which the denominator is multiplied to get 210.

(1×15/ 14 × 15) + ( 1×7/30×7)

= 15/210 + 7/210

= 22/210

Hope it helps.