How do you evaluate #c-2ab# if #a=2.4, b=0.237#, and #c=9.49#?

Question

Julia Adams · Accepted Answer

#8.3524#

Substituting the values we have:

#c-2ab" "->" "9.49-2(2.4)(0.237)# .......................................................................................... Multiplying out the brackets we have:

If the decimals give you a problem and you wish to calculate manually you may do this:

#2.4# is the same as #24xx1/10# #0.237# is the same as #237xx1/1000#

Putting it all together we have:

#24xx237xx1/10xx1/1000 color(white)("d")->color(white)("d")24xx237xx1/10000 #

Multiplying out just the whole numbers: #20xx237->4740 # #color(white)("d")4xx237->ul(color(white)("4")948 larr" Add") # #color(white)("dddddddddd")5688# Now we multiply by #1/10000# giving: #0.5688# giving:

#9.4200-2(0.5688)#

#9.4200-1.1376# ......................................................................................

Changing the way that 9.4900 looks without changing its value

#9.4900" is the same as "9.4cancel(9)^8 cancel(0)^(10)0#

and #9.4cancel(9)^8 cancel(0)^(10) 0" is the same as "9.4(cancel(9))^8 cancel(0)^(9) cancel(0)^10# ...............................................................................

Now we can do the subtraction more easily:

#9.4cancel(9)^8 cancel(0)^(9) cancel(0)^10# #ul(1.1color(white)(.)3color(white)(.)7color(white)(.)6)" "larr" Subtract"# #8.3color(white)(.)5color(white)(.)2color(white)(.)4#

color(white)("d")

Eli Assouline · Answer

undefined To evaluate the expression $ c - 2ab $ when $ a = 2.4 $, $ b = 0.237 $, and $ c = 9.49 $, simply substitute the given values into the expression and perform the arithmetic.

$$
c - 2ab = 9.49 - 2 \times 2.4 \times 0.237
$$

$$
c - 2ab = 9.49 - 2 \times 2.4 \times 0.237 = 9.49 - 1.1352 = 8.3548
$$

So, $ c - 2ab $ evaluates to $ 8.3548 $.