Given that
a:b = 2:3 and b:c = 4:5.
The LCM of 3 and 4 is 12
On multiplying the first ratio by 4 and the second by 3 so that ‘b’ will be the same on both.
So, a:b = 8:12 and b:c = 12:15.
Now ‘b’ is common, we will combine the ratios.
a:b:c = 8:12:15.
Let us combine bridge a:b:c with c:d, holding‘c’ as the common element.
LCM of 15 and 6 is 30
On multiplyinf a:b:c by 2 and c:d by 5 to get c=30.
Again on combining we get
a:b:c = 16:24:30 and c:d = 30:35.
Hence a:b:c:d = 16:24:30:35.