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3 years ago

6. For his history exam tomorrow, Zachary

Mathematics

2 answers:

Nutka1998 [239]3 years ago

4 0

Answer:

I think Zachary studied for 80 more minutes for his history exam than he did with his last exam.

Step-by-step explanation:

2 hr and 40 min = 120+40= 160.

160 / 2 = 80.

This might be wrong also. Not very good with story problems.

3241004551 [841]3 years ago

3 0

Answer:

75 minutes or 1 hr and 15 minutes

Step-by-step explanation:

for history, he studied 2 hrs and 40 minutes....thats a total of 160 minutes

this is 10 minutes more then twice the time he spent on his last exam.

let x represent the time spent on last exam

160 = 2x + 10

160 - 10 = 2x

150 = 2x

150/2 = x

75 = x.......so he spent 75 minutes (or 1 hr and 15 minutes) on his last exam

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$\bold{\huge{\orange{\underline{ Solution }}}}$

$\bold{\underline{ Given \: Rules}}$

The sum of the number in each of the four rows is the same
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$\bold{\underline{ Let's \: Begin}}$

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$\sf{ 75+b+83=76+80+d=a+81+85+78+c+e }$

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From ( 1 ) we got :-

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Subsitute (3) in ( 2 ) :-

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We can write it as :-

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Subsitute the value of c and e in ( 1 ):-

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$\sf{ 158 + b = 156 + d = 166 + a = 189}$

Now, 

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$\sf{ b = 189 - 158 }$

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$\sf{ For \: d , 156 + b = 189 }$

$\sf{ d = 189 - 156 }$

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$\sf{ For \: a, 166 + a = 189 }$

$\sf{ a = 189 - 166 }$

$\sf{ a = 23 }$

Hence, The value of a, b, c, d and e is 23, 31 ,60 ,33 and 51 .

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