If a + b + c = 13, a2+b2+c2=69 then find the ab + bc + ca : 10 30 50 70 a + b +

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Question
If a + b + c = 13, a2+b2+c2=69 then find the ab + bc + ca :
Options
A. 10
B. 30
C. 50
D. 70

Correct Answer

50

Explanation

${(a + b + c)}^{2} = a^{2} + b^{2} + c^{2} + 2 (a b + b c + c a)$

$2 (a b + b c + c a) = {(a + b + c)}^{2} - (a^{2} + b^{2} + c^{2}) = 169 - 69 = 100 = (a b + b c + c a) = 50$

More questions

2. The Shopkeeper increased the price of a product by 25% so that customer finds it difficult to purchase the required amount. But somehow the customer managed to purchase only 70% of the required amount. What is the net difference in the expenditure on that product?
Options
A. 10% more
B. 5% more
C. 12.5% more
D. 17.5% more

6. A number X is mistakenly divided by 10 instead of being multiplied by 10. What is the percentage error in the result?
Options
A. -99%
B. +99%
C. -100%
D. +100%

7. A fair six-sided die is rolled twice. What is the probability of getting 4 on the first roll and not getting 6 on the second roll ?
Options
A. 1/36
B. 5/36
C. 1/12
D. 1/9

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