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Devi and her brother had the same amount of money. After Devi spent 2/5 of her money and her brother spent 3/10 on his money, they had 78$ left

altogether. How much money did they spend altogether?

User NullUser
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1 Answer

3 votes

Let us assume Devi or her brother amount = $x.

Devi spent 2/5 of x, that is 2/5 x.

Remaining amount of Devi = x- 2/5 x = 5x/5 - 2x/5 = 3x/5.

Her brother spent 3/10 of x, that is 3/10 x.

Remaining amount of her brother = x- 3/10 x = 10x/10 - 3x/10 = 7x/10.

Total amount they left together = $78.

Therefore,
3x/5\:+\:7x/10\:=\:78\:


(3x)/(5)+(7x)/(10)=78


\mathrm{Find\:Least\:Common\:Multiplier\:of\:}5,\:10:\quad 10

Multiply equation by LCM 10.


(3x)/(5)\cdot \:10+(7x)/(10)\cdot \:10=78\cdot \:10


6x+7x=780


13x=780


\mathrm{Divide\:both\:sides\:by\:}13


(13x)/(13)=(780)/(13)


x=60

Therefore, each one spent $60 and they spent altogether = 60+60 = $120.



User Mkataja
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