444 x 3 = 1332

1332 is closest to 1330.

Do not round off 444 first before multiplying. Order here matters a lot.

If we round off 444 to 440, we get 440 x 3 = 1320 which is not the same.

Cost of 3 cameras = $444 x 3 = $1332
Round off to the nearest ten since question is looking for the CLOSEST estimated cost.
Ans: (3) $1330

Thanks Eric and Sin Yee.
Ans key put (2) $1320. So i think the ans key got error

Unless they want you to really round off the 444 to make an “easy estimate” on a camera by camera basis before computing the cost of 3 cameras based on each estimated camera.

Noted with thanks Eric:)

The question does not explicitly suggest the value which is estimated.

If a person wishes to compute the total cost and make an estimate, the person would be computing the exact value before rounding it off to say “The total cost is around $1330”.

If a person wishes to compute the number easily for easier multiplication, the person would probably do the round off first.

Here the question is not clear, so I would do a round off at the end.

When you proceed to secondary level, the term “estimate” becomes clearer. Though I would not say that the 1320 option is incorrect (technically it is an estimate after all, in a way), it is not exactly defined well during primary school lessons.

The topic here is estimation. Calculating the exact total cost first and then rounding off to the nearest $10 wouldn't be called estimating. After all, estimating means to 'roughly calculate or judge the value, number, quantity, or extent of'. It serves to provide an approximate value when exact calculation is not possible, inaccessible or too cumbersome.

From the options given,

(1) is obtained by rounding down to $400 and multiplying by 3.

(2) is obtained by rounding down to $440 and multiplying by 3.

(4) is obtained by rounding up to $450 and multiplying by 3.



Another approach to this question could be:

$444 is between $440 and $450

$44 x 3 = $132
$45 x 3 = $135

So $450 x 3 and $440 x 3 is just a matter of adding one more 0 behind, since it's x 10.

Since $444 is between $440 and $450, the actual value should be between $1320 and $1350.

Now, $444 is nearer to $440 than to $450. So this means that $1320 is nearer to and is a better estimate of $444 x 3 than $1350 is.

So maybe that's why the answer key puts it as option (2). It would be correct if the question wants you to estimate like this.




However, $445 is halfway between $440 and $450. So $445 x 3 is also halfway between $1320 and $1350, which is $1335.


And $444 is nearer to $445 than $440. So $444 x 3 is nearer to $1335 than $1320.

We have an option (3), $1330. Since $1330 is closer to $1335 than $1320 is, then $1330 is a better estimate than $1320


So the answer is option (3), $1330


Edit : my approach is in the direction if you were asked to provide the closest estimate without actually calculating the exact cost.

The other tutors' approach would be if you were to calculate the exact cost and then decide which estimate , when provided by someone, is the closest.

It is likely the question is asking for their approach.

Well that’s true, but the word estimate itself can be interpreted differently.

If estimate is a means to make computations easier, 1320 is correct.

But I can say that three cameras cost 1332 altogether, which is estimated to be around 1330.

Your last statement wouldn't be called an estimate. It would be called a rounding off /rounding down. When estimation is done, the exact value isn't calculated. So it wouldn't be 'estimated to be around $1330' but 'approximately $1330'

As mentioned earlier , estimating means to 'roughly calculate or judge the value, number, quantity, or extent of'

Update: Follow J’s explanation.

It’s more of a round-off type of estimate, though it is still an estimate.

Yours and Sin Yee's approach is correct , but it would be addressing the question in this angle :

'Calculate the exact cost of the 3 cameras. Now if someone else were to estimate the cost of the 3 cameras, which of these options if provided would be the closest?'

Either way, (3) is a better answer than (2).

True...