Find the sum of all three digit number which are multiple of 7
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Step-by-step explanation:
→ First three digit term divisible by 7 is 105
→ Last three digit term divisible by 7 is 994
→ We know that tn=a+(n−1)dtn=a+(n−1)d
→ 994=105+(n−1)7 ⇒994=105+(n−1)7
→ n=128 ⇒n=128
→ We know that Sn=n2Sn=n2(l+a)(l+a)
∴ The sum of the required series Sn=1282(994+105)Sn=1282(994+105)
→ =64×1099=70336
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