15) n+4
16) n-6
17) n+3
18)n-2
19)n+6
20) n-8
Step-by-step explanation:
SA=ph+2A, that is, perimeter × height+ twice area
p=21+20+29=70cm
h=22cm
70×22=1540cm
A=1/2 ×20×21=210×2=420
1540+420=1960cm2
9514 1404 393
Answer:
Step-by-step explanation:
If all of Brent's coins were pennies, their value would be 1.63. The value is actually 4.42 -1.63 = 2.79 more than that. Replacing a penny by a dime increases the value by .09. Hence there must be 2.79/.09 = 31 replacements.
Brent has 31 dimes and 132 pennies.
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<em>Solution using an equation</em>
You can write an equation that solve the problem in basically the same way. Let the variable represent the number of coins of highest value: d = dimes. Then the value (in cents) of the collection is ...
1(163-d) +10d = 442
9d +163 = 442 . . . . . . . . . . simplify (note 9 is the difference in value; 163 is the value of all pennies)
9d = 442 -163 = 279 . . . . . . subtract 163
d = 279/9 = 31 . . . . . . . . . . divide by 9
Brent has 31 dimes and 163-31 = 132 pennies.
You justify a step the same way you decided to go through with it:
Remember a rule, axiom, postulate, theorem, or corollary you learned
that says it's a legal thing to do.
Like if you thought of erasing one of the terms in an equation because
that would make the rest of the equation easier to work with, you would
not do that, because no book or teacher ever said that it was legal.
Or if you thought of adding 42 to both sides of an equation, you could
do that, because you learned that "If equals are added to equals, then
the results are equal". Then later, if anybody ever asked you why you
could do that, or asked you to justify your step, you'd tell them the same
statement.