WITHOUT USING A CALCULATER HOW DO I WORK OUT 1.5*2.5*4.
2006-07-13 06:01:58 · 46 answers · asked by babydaddy282000 2 in Science & Mathematics ➔ Mathematics
The easiest way to solve this in your head is to break this up. Try not to multiply decimals together, so start with 1.5x4.
If you have a hard time doing 1.5x4, break that up into:
(1x4) + (.5x4)
4 + 2
6
Now you have 6 x 2.5. Do this the same way, unless you can do this in your head.
(6x2)
12
Now do:
6x0.5
3
Now add
12+3
=15
The easiest way to solve things in your head is to break them up. Don't break them up so much that you can't keep track of all the pieces. Rounding also helps a lot.
2006-07-13 06:12:53 · answer #1 · answered by Dave S 4 · 1⤊ 1⤋
Think of 1.5 as 3 divided by 2, and 2.5 as 5 divided by 2. Then 1.5 x 2.5 x 4 = 3/2 x 5/2 x 4. Gather the numerators together, and gather the divisors together: 3 x 5 x 4 / 2 x 2. The result is 15 -- no calculator!
2006-07-16 20:55:49 · answer #2 · answered by Anonymous · 0⤊ 0⤋
15 4 x 2.5 = 10 then 10 x 1.5 = 15
2006-07-13 06:08:49 · answer #3 · answered by ? 4 · 0⤊ 0⤋
You can say that 4=2*2 so 2.5*4 = 2.5*2*2 which is 5*2 which equals 10. Next you say that 1.5 is 1+0.5 or 1/2. So 10*1.5 = (10*1)+(10/2) = 10+5 = 15.
2006-07-17 08:50:11 · answer #4 · answered by Tom D 2 · 0⤊ 0⤋
I like turning them into fractions:
1.5 = 3/2
2.5 = 5/2
4 = 4/1
So, you get 3/2 * 5/2 * 4/1.
Now, before you go multiplying across, reduce first. Notice that the twos on the bottom will reduce with the 4 in the top of the 3rd fraction. Cross them out (the 2 twos and the 4) and you are left with 3*5 or 15.
The other slick way is to look at it in another order and notice that 2.5 * 4 is 10
Then, 10 times 1.5 is 15.
2006-07-13 06:10:37 · answer #5 · answered by tbolling2 4 · 0⤊ 0⤋
Like any other multiplication but whoever set you this question chose the numbers carefully. If you look at it backwards it becomes trivial and you don't even need to do a single long multiplication.
4*2.5*1.5 = (4*2.5)*1.5
It should be instantly obvious that 4*2.5 = 10
so 10*1.5 = 15
2006-07-14 07:58:53 · answer #6 · answered by m.paley 3 · 0⤊ 0⤋
1.5 x 2.5 x 4 = 1.5 x 10 = 15
2006-07-15 02:33:40 · answer #7 · answered by Anonymous · 0⤊ 0⤋
2.5 * 4 is 10. So to multiply the 1.5 just move the decimal =15
2006-07-13 07:10:49 · answer #8 · answered by famousblue11 2 · 0⤊ 0⤋
I would mentally accomplish this task by converting 1.5 and 2.5 to fractions ... as they are 3/2 and 5/2 respectively ... 3 * 5 * 4 / 2 * 2 = 3 * 5 = 15.
2006-07-13 06:12:41 · answer #9 · answered by Arkangyle 4 · 0⤊ 0⤋
first turn 1.5 and 2.5 into fractions or 3/2 and 5/2....then multiply the numerators across and the denominators across...you should get 15/4...then if you turn the number 4 into a fraction and multiply it should look like:
15/4 x 4/1 = 15
the fours cancel each other out and you are left with 15/1 or 15 as the answer
2006-07-13 06:10:56 · answer #10 · answered by Mike F 3 · 0⤊ 0⤋
Notice that 4=2*2
so that means you can double the 1.5 to get 3, and the 2.5 to get 5.
So now you have 3*5 which is 15
1.5*2.5*4=1.5*2.5*2*2=(1.5*2)*(2.5*2)=3*5=15
2006-07-13 22:40:31 · answer #11 · answered by hi_patia 4 · 0⤊ 0⤋