A sound which has a frequency less than 20 per second is called infrasonic sound. A sound which has frequency more than 20000 per second is called ultrasonic sound.
Solution :
i) 12,15 and 21
12=2×2×3
15=5×3
21=7×3
From the above ,HCF(12,15,21)=3and LCM(12,15,21)=420
ii)17,23,and 29
17=17×1
23=23×1
29=29×1
From the above ,HCF(17,23,29)=1and LCM(17,23,29)=11339
iii)8,9 and 25
8=2×2×2
9=3×3
25=5×5
From the above ,HCF(8,9,25)=1and LCM(8,9,25)=1800
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EXPLANATION:
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